'I became obsessed with the need to find out more about the film, but no one seemed to know anything about it'

I'm a bit of a collector – a hoarder, my wife would say; there's something about auctions that I find irresistible. I collect most things – china, pottery, porcelain, silver, wine, boxes. I was busy on eBay one evening late last year when I stopped, intrigued by a picture of a film canister, considerably battered. "That's old," I thought. I liked it – it looked as though it had seen a bit of life. The bid stood at £3. I placed my higher bid and won it at £3.20.

A couple of days later, the parcel arrived in the post. I forgot all about it for a while and didn't open it straight away. When I did, there was the canister, looking every bit as knocked around as it had in the picture. It felt as if the tin hadn't seen the light of day for many years, and I'm pretty sure that the person who sold it to me had no idea what was inside. I prised off the lid and found a massive roll of old film. What really interested me was the smell – a musty, ancient smell of age.

I took it out, held the film up to the light and saw a familiar figure. "That looks like Charlie Chaplin," I thought to myself. I reached for my magnifying glass and looked harder. There was no mistaking: it was an old Chaplin film.

I was still sitting there gazing at it when a friend turned up and immediately told me not to hold the ancient film up to the sunlight. I had assumed that if it had been around for so long, it would be fine to do so, but I was wrong. One of the first things I discovered about nitrate film was how potentially combustible it can be – it could degrade or disintegrate, even set my house on fire – so I stowed it in a cool box and stuck it out in the garden.

About two weeks later I watched it all the way through for the first time. I'd found a film buff with a specialised machine to show it. There were seven of us; we were in a state of shock, and our buff sat there open-mouthed as we watched images of Chaplin running round pretending his trousers were on fire.

I became obsessed with the need to find out more about the film, but no one seemed to know anything about it. I could see it was called Zepped, so I looked it up. I trawled the internet. Nothing. I contacted the British Film Institute and read Chaplin biographies, but there was no mention of it anywhere. Yet here Zepped was, in my hands, mysterious and unknown.

Finally, I found one reference to it in a translated Russian article that said Zepped had been released in England in 1916. That was my starting point. I went to the British Library's newspaper archive in Colindale and sat there, leafing through old newspapers from 1915 onwards, until my eureka moment.

I came across a report and a poster that explained the film's history. Zepped was an anti-Kaiser comedy, a first world war propaganda film in which Chaplin defied the might of the German zeppelins. At some point it had been shown to British troops in Egypt; I have no idea how or why it disappeared after that.

A good friend in my village used to work in the film industry and he became just as obsessed as I was. I put colleagues in charge of my company and concentrated full-time on learning everything there was to know about Zepped.

We went out to Hollywood to visit Chaplin's old studio and consulted many experts. They were all astonished when they watched it. What I eventually found out was that Zepped – only seven and a half minutes long – is a unique piece of early film history. It was the first film to combine action with animation, much like Mary Poppins, but nearly 60 years earlier.

I don't know what's going to happen next. I have been told that the film could be worth more than £1m, but who knows? I might sell it, but then again I may decide to hang on to it. It's not the money that excites me, but rather the idea that such a random discovery can be so intriguing and historically significant.

Meanwhile, my obsession with bidding for dusty old relics continues – after all, you can come across the Mona Lisa, but it won't stop you appreciating other works of art. Every day there are other treasures out there, waiting to be discovered, but maybe the secret is not looking too hard. When I discovered mine, all I wanted was the canister.

• As told to Sue Mott.

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