Well, it's set in the 60s isn't it?  At some point I had to write something on this most cultish of cult films, and so I thought I'd do a page on some of the questions which I've had about it over the years, and attempt to answer them.  No doubt some of what I come up with will be disputed, but if so then so much the better - better to be talked about etc etc.  

For convenience I have referred to 'I' throughout as Marwood, the name he was given in the script.

If you're reading this, I assume you know the film very well, so I'm not going to waste time with introductions etc.  On with the questions, in no particular order:

1969 obviously, but when exactly?  September, apparently, is the answer; despite Withnail's constant moaning about the 'intense cold', which would suggest that it's January/February time, in response to Withnail wondering what's happened to his cigar commercial, Marwood says "September - bad patch" although this does not placate Withnail, who responds "Rubbish - haven't seen Gielgud down the Labour Exchange."

A further clue is given at the end, when Danny says "We are 91 days away from the end of this decade" which would suggest that this scene takes place on October 1st or 2nd, depending on how you count (ie is Danny counting from the next day or including the same day?).  As this scene is at least four or five days later than at the start of the film (see next section) then the film starts at the end of September. 

We're never told actually, but it is highly likely to be R.C. Sheriff's 'Journey's End'   His auditioning for a part is referred to throughout the film; in the scene referred to above where Withnail reveals his age, he goes on to refer to Marwood's audition:

"You've had an audition, why can't I have an audition?"

and when they go to Uncle Monty's house, after spinning him a line about his theatrical career, Withnail gestures towards Marwood and says "He's just had an audition for rep" (although some have heard it as "Peter's had an audtion for rep", giving 'I''s name as Peter Marwood) although it is strange that Monty never asks Marwood what part in what play.

The big clue is that Marwood is seen reading 'Journey's End' in the cottage after lunch (see above).  I don't know the play at all, but it''s set in the trenches towards the end of the first World War.  When they then go to the pub in Penrith with £5 (?) each from Uncle Monty, Marwood is on the phone to his agent.  As he comes back, worrying that he hasn't heard anything, Withnail says:  "Why d'you want to go to Manchester anyway to play a bloody soldier?"  When Marwood tells him that he's very keen, and that it's a good little theatre, Withnail mentions that "it's not much of a part though is it?"  Marwood replies "It's better than nothing" at which Withnail says again "They'd make you cut your hair off!"  Marwood then makes the cryptic reply "So what, you'd lose a leg!" which can only be a reference to another character in the play, although Withnail has not auditioned for it.

On their return to London, Marwood rings his agent, and finds out that he's been offered the lead role, and in the next scene he has indeed had a haircut.

This question must surely remain unanswered.  Danny lets them have a bottle contraption when he first comes round; he says that he is thinking of going into business in the toy industry.  Withnail cynically comments that he thought Danny was in the 'bottle industry' but Danny says that that is just a sideline, and, indicating the Fairy Liquid bottle with tubes coming out of it next to him, says nonchalantly "You can have that.  Instructions are included."

It is not referred to again until the next day, on the way to the cottage, when Withnail says that he wants to stop and get hold of a child.  When Marwood asks why, Withnail replies, firstly "to tutor it in the ways of righteousness" but mainly to get hold of some uncomtaminated urine.  He then explains to Marwood how the bottle is meant to work, reading from the brief instructions written out by Danny, "allowing the drink-driver to operate in absolute safety", providing a clean urine sample (having refused everything but a urine sample), with the result that "they have to give you your keys back".

Sadly for Withnail but possilby thankfully for the rest of the British motoring public, he is inevitably caught out at the police station (see pic above); I was fascinated to read of an Italian athlete, Devis Licciardi, trying something similar (presumably a bit more sophisticated though) in 2013, where there were explicit references to Withnail and I in the story:

"An Italian long distance runner is facing disciplinary proceedings for allegedly using a fake penis to beat a dope test.  Devis Licciardi, 27 is said to have used a realistic-looking prosthetic containing uncontaminated urine to give a sample following a 10km road race.  The allegation echoes a farcical scene from the film Withnail and I, where the titular character tries to avoid a drink-driving arrest by passing off a child's urine as his own."

This doesn't answer the question of where Withnail gets the urine from.  Although all he has to do is use his own urine, he of course would have the problem of it being uncontaminated, and as we have seen above that is quite a problem for Withnail.  It reminds me of the episode 'One for the Road' in 'Whatever Happened to the Likely Lads?', where Bob is so worried about losing his licence for drink-driving that he gratefully accepts Terry's offer of swapping urine samples; only later does he stop to consider how much Terry had had to drink....

Usually writers say that such iconic characters are based, not on one individual, but on an amalgam of different people, but in this case the answer is clear and well-documented now; Withnail was based on one Vivian MacKerrell (1944-1995) with whom Robinson shared a flat in the late 1960s, along with Michael Feast and David Dundas.  Little still seems to be known about MacKerrell - he was only in one or two films or TV plays, and no stage roles have been mentioned in anything I've read - and Robinson has, to the best of my knowledge, never talked about his relationship, if indeed there was one, with MacKerrell after he left the flat, as Marwood does at the end of the film.

In particular it would have been very interesting to know what MacKerrell thought of the film when it came out - presumably he recognised himself in the character - but again there is only silence on this subject, although there is a book out - a biography of MacKerrell - by Colin Bacon called 'Vivian and I', which I'm going to try and get hold of, which might answer some of those questions.

Bruce Robinson wrote a touching tribute to MacKerrell at the start of the edition of the published screenplay:

"That night we go into Regent’s Park and look at the wolves. I can’t count the number of times we went into the park and looked at the wolves. And I can’t believe that Vivian is dead. He got cancer of the throat and they tore his voice out. And the fellow I’d always thought of as being the biggest coward I’d ever met materialised into the bravest bastard I’d ever known. It’s got to be hard to laugh when you’re dying, but I’ll always remember you laughing. That sad, brilliant, bitter face of yours laughing. Goodbye my darling friend. This is for you for ever. And I know if there’s a pub in heaven, you’ll be in it. And Keats will be buying the drinks."

Here's Robinson and Richard E Grant discussing the origins of the Withnail character in the documentrary 'Withnail and Us':

Until quite recently, I wondered if I was the only person with a theory on this, as nobody else seemed to mention it, or discuss it anywhere.  This seem highly unlikely though, given the hundreds if not thousands of sites and blogs devoted to the film, and indeed recently I have seen a number of posts and blogs referring to the scene and its meaning.  For me, the end refers back to the scene near the start of the film where Uncle Monty, with "little more than vintage wine and memories", opines that:

It is the most shattering experience of a young man's life when, one morning, he awakes and, quite reasonably, says to himself: "I will - never - play - the - Dane."  When that moment comes, one's ambition ceases.

Withnail replies immediately:  "It's a part I intend to play Uncle" and Monty assures him he would be marvellous.

However, as he performs in the park in the pouring rain, to nobody but the wolves, it is evident to all that this is the nearest Withnail will ever get to performing the role, and the film ends in quiet desperation and sadness.