"Early doors" - is especially associated with English football, and with commentator Ron Atkinson in particular - one Telegraph writer wondered "Does Big Ron ask his wife if she might get breakfast ready early doors?" A couple of books, though, suggests its football use started in 1979 with Brian Clough, in an interview, - "Early doors, it was vital that they (the players) liked me" (Who Invented the Stepover?:and other crucial football conundrums, by Paul Simpson, Uli Hesse)

It is apparently now popular with commentators, footballers and fans alike. It seems to me as if it probably started off as an in-joke among the footballing fraternity, and just stuck. Its history goes back well before its use in football, however, with its roots in nineteenth-century theatre, where by paying a premium you could go in early and avoid the crush - this was known as 'early doors'. There are a couple of books about old Music Hall with this phrase in the title .

A letter-writer to the Telegraph remembers his grandparents using it like this in the 1930s. In fact there seems to have been quite a lot of discussion about the phrase in the Telegraph.

http://www.google.com/search?hl=en&q=early+doors&gws_rd=ssl#hl=en&q=%22early+doors%22+site:www.telegraph.co.uk

By 1908, the expression had reached Australia: this is from the New South Wales parliamentary register for that year - "The swindle was worked in this way : people who wanted to get decent seats in a theatre waited outside in queue order, and had to pay an additional shilling for early doors." Six years later, in the Australian parliamentary records, this appeared: "We have been told that it was a packed meeting which was held in the Sydney Town Hall—that. is to say, that the hall would not hold more people, that the early doors were rushed".

There's another theory that it was what people who arrived early at pubs after afternoon closing were called, an idea picked up in the title of a BBC sitcom called 'Early Doors', which is set in a pub. In another letter to the Telegraph, the witer suggests that it is often used with that meaning in the Midlands - "I'll meet you in the Red Lion, early doors."

In his dictionary of slang, Eric Partridge apparently thought it was Cockney rhyming slang for women's drawers (the undergarment), dating it from 1870.

G.K.Chesterton, amongst others, pointed out that it was a British battle cry in the First World War. This is from a pamphlet, The Retreat from Mons, published in 1914 - "A party of the King's Own went into one battle shouting out, 'Early doors this way! Early doors, ninepence!' ". And from the Fortnightly Review of 1917: "I cannot imagine any but a British regiment rushing into the hell of the machine-gun fire with the cry of 'Early doors sixpence extra' ".

Returning to sport, it's obviously spread beyond football: here is rugby player Will Greenwood writing in the Telegraph - "One black mark: he should have scored early doors, he must learn to get them down." And the Telegraph even used in the financial pages (I presume tongue-in-cheek) - "It's early doors for the Grand National bookmakers" (the favourite had won the National).

You can read about it here - http://www.worldwidewords.org/qa/qa-ear1.htm

The history of English expressions can be rather fascinating when you start Googling around and looking in Google Books. Given its varied and colourful history, I've rather warmed to this phrase.

I don't quite follow the question - I don't see that's it ambiguous in any of these. Sarcastic (f), over-generous (g), cheeky (b), perhaps, but ambiguous? Perhaps the guy in (g) is being ironic, but you never know nowadays.

But in the title it asks when it's impolite, which is rather a different question, and as Jasper said, that depends on intonation, or what else is said (as in the police example).

No safer, perhaps, but "be my guest" or "go ahead" would work for a, c and g. Or perhaps "Mi mujer su mujer" for g?

A note on the grammar - it seems we were barking up the wrong tree when talking of gerunds: 'missing' is generally regarded as an adjective here (just check missing in any dictionary, for example - http://thefreedictionary.com/dict.asp?Word=missing).

Did you ever find that missing piece of the jigsaw puzzle?
He was reported missing last year.
The missing child was found safe and sound.
My gloves have been missing for ages.

So 'missing' in this expression is ana adjective in predicative positions and go' is indeed acting as a linking or copular verb here, functioning grammatically like 'be':

She is missing.
She went missing two weeks ago.
She has gone missing.

Here 'go' has more of the meaning of 'become', another linking verb, as in the expressions porsche and I have already pointed out, as well as one or two others:

She is crazy about him.
She has gone crazy.

It's very dark.
It suddenly went dark.

He is bald/blind/mad/bankrupt etc
He has gone bald/blind/mad/bankrupt etc

His hair is grey.
His hair has gone grey.

This milk is sour.
This milk has gone sour.

The children are really excited.
The children went wild with excitement.

This is all wrong.
Everything went wrong.

But admittedly, 'missing' is the only adjective ending in '-ing' that I can find being used with 'go' in this way.

@DesertRat71 - ' "Gone missing" has a "street" ring to it and causes the person saying it to appear lacking in education. If this is the sort of thing they were taught in school it's an indictment of our education system. Then again, maybe they're attempting to appeal more to the uneducated.' - You don't actually say why you think this is wrong, so we have to do a bit of guesswork.

If it's because go is being followed by a gerund, as Jasper has pointed out, many verbs are followed by an infinitive or gerund. You'll find lists of these if you Google "verb patterns". Go + 'ing' form is common in talking about sports and activities - "go fishing, go cycling"etc.

But, as is perhaps more likely, your objection is that "go missing" is not a deliberate action, you would seem to have some support from GrammarGirl here. On the other hand "go" is often used as a linking verb for describing events over which the subject has no control - "go bald, go grey, go numb" etc.

As has been mentioned a couple of times above, this is a British idiom, which for us Brits is absolutely standard, and quite old. Here are some 19th century examples:

"That was the letter that went missing ?" - Victoria Parliamentary Papers (Australia) 1859
"the marshal requested the stranger to tell the true reason for his refusing to be searched when the snuff-box went missing" - Short stories 1876
"Not an accident occurred under his care, not a piece of baggage went missing" - Crusading with Knights Templar, Pennsylvania 1878
"But I know that if they went missing I should feel pretty happy" The Granta 1890

But recently it has begun to appear more and more in American publications, and it does seem to be something that grates on some American ears.

It is perhaps worth quoting the famous William Safire, writing in his 'On Language' column in the New York Times in 2004:

"Why has the construction lasted so long and now blossomed? It does a semantic job that needs doing, that's why. No other term quite encapsulates ''to become lost inexplicably and unexpectedly,'' which connotes suspicion of trouble. From the most serious loss (a person kidnapped, or a soldier unaccounted for or absent without leave) to an irritating minor loss (an object is mislaid), to go missing -- always in its past tense, went , or past participle, gone -- conveys a worried, nonspecific meaning that no other word or phrase quite does.

Is it good grammar? It may well stretch our hard-wired sense of syntax. To critics, a simple is missing would solve the problem. But because gone missing has acquired the status of an idiom, which is ''an unassailable peculiarity,'' it is incorrect to correct it. As the fumblerule goes, ''idioms is idioms.'' Relax and enjoy them." (http://www.nytimes.com/2004/06/27/magazine/27ONLANGUAGE.html)

There are discussions of this question at these linguistics blogs:

Separated By a Common Language:
http://separatedbyacommonlanguage.blogspot.com/2009/12/words-of-year-2009-staycation-and-go.html

Not One Off Britishisms:
http://britishisms.wordpress.com/2011/02/20/go-missing/

Language Log
http://itre.cis.upenn.edu/~myl/languagelog/archives/001142.html

@HS - that puts you pretty well in line with Prof Brians at WSU (link above). But is it very far from saying "this is the key to our success" to "this is key to our success"? Yes, you could say "vital" or "crucial", but I see nothing wrong with having another arrow in the quiver.

I forgot to say earlier, when I said 'key' (before a noun) was short and punchy, that I just don't see how that can be thought 'pompous'. I suppose I see "key" used so much in business contexts that I've never even thought about it and take it for granted that everyone knows what it means - my students certainly do. It's pretty normal these days to talk of key clients /key accounts, key objectives, key markets - all of these expressions have been used in the Economist, which is good enough for me. If anything it seems to me to be a shorthand word rather than a pompous one.

But I suppose that at least I've learnt a new word, or at least a new meaning of a word - 'poop' (Number 5 at Oxford Online).

@Jasper - I get that, especially after "but", but it's a bit odd to trail off after "no problem", isn't it? No problem is usually said in quite a bright breezy way, I would have thought. However, as this use of ellipses is totally new to me, perhaps I should just shut up.

@jayles the unwoven - but surely "No problem" is in itself a complete utterance. We might say "That's no problem", but we wouldn't normally follow "No problem" with anything, would we? Except, perhaps, "mate", or something similar. I don't know about the writer being upset, but that ellipsis looks distinctly odd to me. It looks as though they want to add something or leave something unsaid.

That should of course read - "If he were to move his arm" means exactly the same as "If he was to move his arm", the only difference is one of formality.

@Jasper - "Although my Word (not always the best basis to go by) tells me that "was" should be "were", I however cannot see how this would be an unreal conditional. First, the action hasn't taken place yet; second, it doesn't seem impossible/counterfactual in the condition clause; third, only the result seems impossible; and finally, I had written the character to move his arm in the very next sentence with nothing happening."

Your sentence was "He was convinced that [if he was/were to move his arm, it would break]."

By using the "was/were to" construction, you yourself have decided to use a counterfactual: that's what the "was/were to" construction is. And as I said before, purists (and your spell checker) , will demand subjunctive "were" there, though EFL teaching is more tolerant. But whether you use "were" or "was" in this construction, it is still a counterfactual. "If he was to move his arm" means exactly the same as "If he was to move his arm", the only difference is one of formality. Just as "I wish I was in Egypt" is no less of a counterfactual than "I wish I were in Egypt" - it's just the use of "was" instead of "were" is increasing (which is presumably why the Egypt's ad agency went for "was").

"Was/were to" is often used to make a suggestion more tentative:

"If I take 100 items, will you give me 5% discount" - real conditional
"If I took 100 items, would you give me 5% discount" - an unreal (counterfactual) conditional to make the suggestion more tentative
"If I were to take 100 items, would you give me 5% discount" - an unreal conditional, even more tentative.

I think we can prove that this is a possible subjunctive as we can invert it (but only the "were" version):

"Were I to take 100 items, would you give me 5% discount" (NB we can't do this with "was")

This is from Longman's Dictionary:

"used in conditional sentences about an imagined situation - were somebody to do something/if somebody were to do something

'Even if England were to win the next two matches, Germany would still be three points ahead.'

'Were we to offer you the job, would you take it?'"

There's also a bit about "was/were to" at Wikipedia:
http://en.wikipedia.org/wiki/English_conditional_sentences#Second_conditional

So, taking on board what you've said about this being a real conditional, I would drop the "was/were to" construction altogether and simply write "He was convinced that if he moved his arm, it would break."

A couple of links, one more or less taking the side of those who don't like 'key' as an adjective:

http://www.grammarphobia.com/blog/2007/07/key-bored.html

And a fairly neutral one about adjectives being formed from nouns at the Macmillan Dictionary blog:

http://www.macmillandictionaryblog.com/noun-like-adjectives

Skeeter Lewis - I agree that this could sometimes be confusing when talking about age (although, as usual, context is everything), but just to mean only has a long history, and I see no problem with things like "It's just another mile or so"

A quick site search suggests that "was just 18" as opposed to "was only 18" is rather more popular in the British tabloids than in the qualities (although it certainly exists there as well). Ngram does indeed suggest that the use of 'was just 18' to mean 'only' has certainly increased since the 1960s, but you can find examples from the eighteenth century in Google Books, although it's difficult to tell whether there is a recency factor or not.

You're probably right about fashions, and that can be annoying, but I don't think that makes words or expressions bad in themselves. And secondly, just because we already have one word for something, I don't see that as a reason for not using others as well. As someone remarked on another thread, that we would always say huge and never enormous.

Going back to "key", I think jayles nailed it on the head when he said that it's short and punchy - so we have "a key venue" rather than "one of the most important and prestigious venues" (it was also built specially for the games and quite expensive).