Last spring I bought a bar of Pears soap. Ordinarily, its fragrance is redolent of fresh laundry, clean white sheets and accumulated cosy memories; this bar was more reminiscent of burning rubber and recycled cooking oil. So I bought another bar – same problem. A quick Google revealed that Pears soap, which I've used all my life, had been transformed by Unilever into a disgusting new formula that smelled as if it was produced in the same factory as Pot Noodle and Domestos.

Products come and go. And formulas change, too – think of Tizer and Mars bars. We think we'll never get used to the new variant, but we do. Pears soap, however, is the oldest continuously existing brand in the world, having first been registered in 1789. Most significantly it has always had very few ingredients, and was hypo-allergenic, meaning a delicate soul such as myself could use Pears alone of all high street brand soaps. It still claims to be hypo-allergenic but now the list of ingredients rivals Sunny Delight.

So, over the summer I started to buy up as many "original" Pears soap bars as I could. Any chemist I passed, then any corner shop, was sniffed out for old stock. If I had a spare couple of hours I scoured a new London suburb; on a summer holiday in Yorkshire I rated towns on how many Pears bars I could find there (Tadcaster won with 14). During the World Cup game between England and Slovenia I made an excuse to leave a friend's house at half-time and returned with 22 bars. I built a pyramid of Pears soap in my bathroom; visitors claimed to be impressed. When should I stop, I wondered? I started calculating – if I use a bar a month, if I live to be 80 . . .

My guess is that Unilever is trying to phase Pears out altogether, and encourage the world to use Dove, which it also makes and is the only soap many chemists seem to stock. Some don't stock soap at all, only shower gel and liquid dispensers.

Anyway, all supplies of old Pears now seem to have dried up, so I can spill the beans without anyone else getting the same idea. It's all mine. I'm pretty sure I have enough Pears soap to last the rest of my life.

Unilever did amend the new formula to improve the scent following a Facebook campaign, but we're still not back to the original, so I'm imagining a future for myself as a dealer in rare Pears: I could slice them up and sell slivers at inflated prices to pay the mortgage. In 20 years the Pears standard could rival the gold standard.

And if Unilever does back down and relaunches the original soap as "Pears Original" or "Classic Pears" or "Pears Soft Face Solutions", at least my bathroom, thanks to the 200-plus bars I've hoarded, will always smell like freshly laundered linen.