The first time I met Del Boy was 40 years ago.
Syd Lotterby, the producer of Open All Hours, in which I was co-starring with Ronnie Barker, pressed a large-ish manila envelope on me.
In a very casual way, he asked if I'd be prepared to have a look at its contents.
That evening, at home in my flat, I pulled out the script for episode one of something called Readies, by John Sullivan (the name change came later).
Straight away I got a good feeling about what I was seeing.
The first time I met Del Boy was 40 years ago, writes David Jason (pictured middle, with Nicholas Lyndhurst, left, and Lennard Pearce, right)
The hurling of insults between characters is a sitcom staple, but the insults between these particular characters seemed to have a different class of cut and thrust about them.
I started to feel that certain twitch you get when you first read a punchy script.
I was particularly drawn to an exchange between Del and his much younger brother, Rodney.
Del says: 'For the first three months of the pregnancy, you were treated as an ulcer. And to this day I sometimes think the original diagnosis was correct.'
Could I see myself as Del? Could anybody else, for that matter?
I wasn't the original choice for the part: Enn Reitel, a great comic actor and voice specialist, was apparently the first port of call.
He was busy on something else, so Jim Broadbent was offered the role. He turned it down because he was about to start work in a play.
I'm told that Robin Nedwell, of the Doctor In The House comedy series, and Billy Murray, who was later on The Bill and EastEnders, may also have been considered.
Being tall, both Enn Reitel and Jim Broadbent would, on the face of it, have made a more plausible brother for Nick Lyndhurst (David Jason, right, pictured with Lyndhurst)
There could well have been others. Why, perhaps you, dear reader, were offered the role, too, and turned it down. It would hardly come as a shock to me.
By the most conservative estimate, I was merely the fifth option on the list headed: 'People the BBC would be interested in talking to about playing Derek Trotter.'
I suppose I could have been offended.
Some actors, I'm sure, would have been terribly sniffy about not being offered something first, let alone being offered something fifth.
But I was 40 and a bit of maturity helped. My attitude was: I understand all the reasons why you didn't come to me first.
Now I'll show you why you should have done.
Being tall, both Enn Reitel and Jim Broadbent would, on the face of it, have made a more plausible brother for Nick Lyndhurst.
But it was better that Del and Rodney didn't resemble each other. I remember, in the earliest proper meeting I had about the show, saying: 'One of them could be the milkman's.'
And there was that wonderful insinuation throughout the show that Rodney and Del might not share a genetic father — the notion, never overplayed but hovering in the background, that it's only the two of them who really believe they are full brothers.
Everybody else has their doubts.
It mattered, too, that Del was smaller than Rodney. The smaller man punching up is always funnier than the bigger man punching down.
Without that disparity in height, some of Del's bossiness could have looked like bullying.
Bear in mind that John Sullivan wrote the entire first series without a single role having been cast or a single scene tried out.
It's why comedies so desperately need time — time today's broadcasters don't have the patience to give them.
By the most conservative estimate, I was merely the fifth option on the list headed: 'People the BBC would be interested in talking to about playing Derek Trotter'
With the first series recorded, John could start writing for the characters as they were played.
He could have us — our faces, voices, bodies — in his head as he wrote. The writing could only get better.
For the second series, the title music was changed, from the typical sitcom theme that had been commissioned from Ronnie Hazlehurst to the now familiar tune and lyric that John wrote (and sang).
John had that music ready for use with the first series but it was declined.
Now, though, people at the BBC saw the value of a tune that in some way helped to explain the series and got people over the hurdle (apparently still a problem) of the obscure title.
Even then, the second series performed fairly indifferently. Viewing figures again hovered around the seven to eight million mark — and the axe hovered over the show.
John was convinced, from conversations he was having at the BBC, that he was being gently nudged to ditch Only Fools, move on and come up with something new.
We'd had two bites at the cherry now. It looked extremely unlikely anyone would offer us a third.
But then came one of those unforeseeable developments. The second series was repeated, without fanfare, and its audience began to grow.
The second time, it caught on.
People began to see what those of us close to the show thought we could see from the beginning: that this was a seriously great set-up.
But then came one of those unforeseeable developments. The second series was repeated, without fanfare, and its audience began to grow (pictured, Del Boy's van used in the show)
It raced on from there and the rest is history: record-breaking Christmas specials and audiences of 24.3 million that practically stopped the national electricity supply when everybody headed for the kettle afterwards.
Many is the time I've wondered why the programme should have struck so deep and lasting a chord with people.
But I have a theory about one little thing that may have been a contributing factor.
People often talk about the warmth of Only Fools and a lot of that, I'm sure, comes from the fact that there was a small cluster of people at the heart of the show who were sympathetic to the background; who had a relationship with working-class life in London.
John Sullivan had grown up in a small terrace house in postwar Balham, the son of a plumber and a cleaner, and had an upbringing similar to mine.
And Ray Butt, the director, was another London boy who had worked on a stall in the East End with his father.
A few of us, then, knew something about what it was like to come from that kind of place, to sense the limited expectations that were laid out for you and to find yourself doing a bit of pushing and shoving to 'get on'.
Perhaps that's a small but crucial part of why Only Fools rang true and made the connections it did.
I don't think any of us in the cast was quite ready for the kind of fame that would descend on us as a result of Only Fools And Horses.
How could we be? Its success was utterly unpredictable.
When a show begins to take an audience along with it, that's an extraordinary thing to find yourself caught up in.
You can feel the heat around the programme beginning to intensify.
The first inkling you get is when strangers start repeating lines back to you in the street. 'Oi, Del,' people would say to me, straight off the bat. 'Where's Rodney?'
'Rodney!' people would call out to Nick Lyndhurst. 'You plonker!'
They meant it in the nicest possible way. But for Nick it was quite some reaction to generate simply by walking up the road to the shops for a paper.
'All right, Dave?' The late, great Roger Lloyd-Pack used to hear that line of his coming back at him constantly — and in the obscurest places, including, he once avowed, from a man he'd never met, walking the other way in the middle of a raging blizzard in Iceland.
It was late and Roger was wearing an anorak with the hood up. 'All right, Dave?' said this Icelandic stranger, before he passed by and headed on into the night.
Anyway, for many reasons, I wasn't sure whether to go when I was invited at the start of this year to the annual Only Fools convention, at a hotel in Bedfordshire.
Worries about letting people down were prominent in my mind. Wasn't I bound to disappoint the conventioneers? I was so much younger when those programmes they remembered so well were made. I had more hair, and other things in my favour.
All these people would be expecting to see the bloke who did all that funny stuff in Only Fools, and then this ageing primate walks in ...
All this was spinning around in my head as I pitched up at the 'stage door' at the back of the hotel at 8.30am on the Saturday.
As the morning wore on, there was a growing crowd of fans and I began to feel nervous in a way I hadn't felt in years.
When I appeared, there was a gale of applause and cheering to the point where I was looking over my shoulder to see who else had come on behind me.
What swirling emotions the following hours stirred up.
I had thought I didn't need to go to a fan convention to know what the show meant to people.
I felt I knew that already, from people coming up to me in the street, or writing to me.
I knew how much people felt the characters in that show spoke to them.
I had more than once been asked to record a message in the voice of Del in the hope that, played at the bedside, it might bring a loved one out of a coma.
That request pulls you up short, let me tell you. I had done as asked, too, and on at least one occasion had been assured that it worked.
Then there were stories like the one I heard about Keith Drew. In 2016, Keith, who was from Frome, in Somerset, died at the age of 76 from leukaemia.
In accordance with his wishes, his coffin arrived at Haycombe Crematorium in Bath in the back of a Reliant Regal, chopped and extended to become a yellow hearse, with Trotters Independent Trading on the side.
New York, Paris, Peckham — and now Haycombe Crematorium.
The coffin was borne in to the show's theme song — a choice of ceremonial music that, I am led to believe, is made quite often: not quite enough to rival Robbie Williams singing Angels, maybe, but up there somewhere.
I heard about the Drew family's plans and felt I could only send them a letter of condolence, in which I made a version of the remark I have found myself making so many times over the years: 'It is amazing the show has meant so much to people.'
Next, I added: 'If the vicar is wearing a hat, tell him to keep an eye on it. I am sure your dad would appreciate that thought.'
I knew they would get the reference and maybe you do, too. It's one of my favourite John Sullivan moments — Grandad's hat lobbed solemnly into his unfilled grave at the funeral by an ashen-faced Del and Rodney — except that it wasn't Grandad's hat, it was the vicar's.
To build a moment of deep poignancy, then softly undermine it in a way that is hugely funny but leaves that poignancy intact, seems to me as good a mark as any of John's facility as a comedy writer.
John Sullivan's writing never shied away from the big things in life. Birth, love, marriage, death and everything in between found its way into the drama, and I knew people associated the show with big moments in their own journeys.
But meeting all those fans face to face across a weekend took my appreciation of the relationship people have with the show to another level completely.
It was joyful, it was sobering; it made you proud, it made you humble.
Some people who came and sat down beside me were in tears and could hardly get out the words they wanted to say. I thought about that a lot afterwards.
Some people told me they had been in a very dark place and that they felt the show had dragged them back from the edge.
More than once, I listened to someone thank me for, in effect, saving their life. Which is something to hear in a conference suite in Bedfordshire on a Saturday afternoon.