Dom Joly: You're in trouble when they melt your head

I had to get a mould of my head made last week. I'm about to start filming something in which I will need to be in disguise. For this disguise, I need to become an even older man than I am – hence the visit to the prosthetics experts.

The first stage involved the making of the death mask – "we prefer to call them life masks" they said politely. This meant covering my head in plaster until I could only breathe through my nose. Apparently some people have found this claustrophobic, staggering around the room trying to rip the stuff off.

I found it rather relaxing, like being in a warm cocoon. So much so, in fact, that I almost resented the moment when they carefully peeled it off and I was dragged back to reality. As I adjusted to the light, I stared at the wall in front of me on which hung loads of properly famous faces that had been through the same procedure.

It was quite weird: a surprisingly big-lipped Meryl Streep, a peaceful-looking Oliver Reed (who looked a lot like a drunk Eddie Izzard), Sean Connery, Liam Neeson. All these faces stared back at me accusingly – wondering what on earth I was doing there? I felt very small.

This is not my first time having prosthetics. For my old BBC1 show I got turned into an 88-year-old man who looked worryingly like Alan Whicker's evil brother.

The disguise was incredible – so good that at the end of the filming day I knocked on my mother's door and pretended to be some crusty old colonel canvassing for the BNP. She didn't recognise me and happily (for me) sent me away with a flea in my ear for being from such an odious organisation.

I wanted the same people to do my prosthetics this time but, rather embarrassingly, it turned out that they had "disposed" of my head mould, which is why I needed to make a new one. This is a bit like being melted down in Madame Tussauds and turned into Keith Lemon. It's never the greatest sign of confidence in your career when a decision is taken to jettison your head.

That's showbiz. I remember when some merchandiser once approached me with the idea for a mobile-phone holder in my image. He brought a prototype with him. Curiously my plastic effigy was sitting in a cinema chair and eating popcorn while screaming into my big mobile. Since I'd always filmed the mobile sketches standing up, this struck me as rather odd.

All was revealed however when I looked at the on/off switch. It said, "Ricky will need 10 seconds to re-set if turned off and on." They'd simply turned Ricky Tomlinson's character from The Royle Family – the one that never leaves his chair – into me. By now I'm sure that I've been melted down into Ricky Gervais who is currently being turned into Miranda, the new queen of everything that's funny.

Back in the prosthetics studio and it was nearly time for me to leave. I asked them what Ollie Reed had been like to work with? "Great fun," they said hesitantly. "He was very nice but insisted on getting up every 15 minutes and dancing around and having a sing-song. He wouldn't sit back down until we all joined in."

I told them my favourite story about Keith Moon visiting Ollie Reed in his new helicopter and Reed greeting him by trying to shoot it down with a shotgun. We all nodded in smiling agreement that the days of "proper showbiz" were long gone. Nowadays it's all sex-texting and Twitter trolling. It's enough to make Ollie Reed give up the drink, were he still around.