"I look at this photograph, taken at Prince Charles’s 60th birthday gala at the New Wimbledon Theatre in November 2008, with mixed emotions.

Half of me feels very lucky and privileged to have shared that moment performing with one of the greatest talents in the history of comedy, but the other half feels terribly shocked 

that Robin got to the point of feeling so sad and defeated that he couldn’t see a way out.

I’d already been asked to do the gig but hadn’t planned any material, and I was dealing with something mundane like ordering a skip for a rubbish clearance and waiting for them to call me back.

The phone went so I answered it quite abruptly, expecting it to be the skip firm, then this American voice said, ‘Hi, this is David Steinberg, 

I’m Robin Williams’s manager and he wants to do a song with you.’I was like, ‘What? What?’ It was totally out of the blue and it was extraordinary. 

We’d never met but I’d admired Robin for decades and I was in awe of his lightning-quick mind, his improvisation skills and his irrepressible onstage persona.

We met a couple of days before the show at his central London hotel to rehearse and hit it off immediately. In between doing impressions of the Queen, Robin was very kind and welcoming and we had such a laugh rehearsing.

We decided on a blues number – he was actually a great singer – and, after knocking some ideas around, came up with a funny line about the Queen having two birthdays and Charles only having one.

On the day itself, the whole venue was locked down for security so we and loads of other comics, including John Cleese and Eric Idle, were holed up all day and there was a slightly giddy Gang Show mentality.

The most surreal moment was during the warm-ups, which are normally very quick.

During mine, I noticed Robin was in the audience watching me and he started saying, ‘Go on, do some stuff,’ and I suddenly found myself doing an impromptu private gig for Robin Williams. Unlike some comics, who can be very critical of the competition, he was so warm and supportive.

He was also exactly the same offstage as he was on it: firecracker wit and a razor-sharp mind. He was riffing, coming up with ideas, making jokes but not in a way that he was trying to cut you out. He was trying to add to what you were saying and keep the flow going. He was a brilliant foil and constantly buzzing.

I loved his relentless energy but I can’t imagine being like that all the time and I suppose it’s inevitable that there’s another side to that. 

I didn’t sense any sign of sadness but perhaps on his own, in his quieter moments, he would have tremendous lows that would match those tremendous highs. Perhaps when there was no one around to constantly entertain and delight and enchant with his constant ideas, maybe then he would feel the inevitable downside of that cycle.

We chatted about comedy a bit at the aftershow party but I never saw Robin after that night. There was some talk through our managers of me possibly going to the States to do some shows with Robin but, for whatever reason, we couldn’t work out any suitable dates. 

When I heard news of his death in August 2014, I was so sad and shocked. I thought, ‘What a terrible waste.’ Creatively, it felt like he was enjoying a second wind – and as a comedian watching another comedian he was so obviously loving what he was doing. It’s such a shame to see that brought to a premature end.

But sad though I feel when I look at this photo, I will never forget the sense of spontaneity and joy he exuded and my time with him reminds me of why I went into comedy in the first place. He’ll be greatly missed.”

 Bill’s brand new live show, Larks In Transit, is touring from January 29 to June 16. For details and tickets, visit billbailey.co.uk.