My signed tie is up for auction. I don’t think even my mum would buy it

‘Surely there’s nobody barmy enough to have troubled themselves to counterfeit the thing.’ Photograph: the saleroom

Whenever I see a signed this or that for sale, I ask myself why anyone would want it. Apart from anything else, unless you were standing next to the celebrity when they wrote their name down, how can you know it’s genuine? With that in mind, I wish to vouch for the authenticity of one unique piece of memorabilia.

A friend, quite beside himself with mirth, has sent me details of lot 4238 in an auction next week. Though it was only a WhatsApp message, I swear I could discern the marks from the splashes where his tears of laughter fell.