Tesco stinks, Sainsbury and Waitrose deliver; with a salute to Rory Sutherland

Unless you're in the business or slightly mad I don't suppose you spend much time following the battle between the supermarkets - but I am slightly mad, and occasionally hopping mad, too.

Last year I bought some foul smelling cod from Tesco, but they wouldn't give me my money back. There was a message on the receipt asking me to tell them how my "shopping experience" was - but when I told them I never even got a reply. When I had the same trouble with Sainsbury they gave me my money back - and a gift voucher.

Today I bought a sandwich from Waitrose and on the package I read a promise that if I was not satisfied, they would refund my money and give me a replacement. I had to read it twice to make sure. Yes: they'll give you your money back and a new sandwich.

People talk about "killer apps". That's what I bet is a killer guarantee.

People greatly underrate the power of the guarantee. Generally if you offer something good, the stronger your guarantee the better you'll do. Our cousins in the U.S. have, as ever, coined a fancy name for the reason why this is so. It is "risk reversal". The stronger the guarantee the less people worry about putting their hands in their pockets.

Waitrose sales for the week ending October 15th were 11.7% higher than the same week last year

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I am just recovering from my annual nightmare - EADIM. What makes it a nightmare is not just the fear of everything going wrong, it is that sitting through all the other presentations, which I always do, is a bloody sight harder than making my own.

It's not half as hard, though, as what Rory Sutherland did on Thursday - fly in from New York, go home to freshen up then come and give us two hours of wisdom and hilarity in equal measure. A hero.

The big surprise from me this year was that less than half the delegates were from the U.K. and that it's almost impossible to get a decent bottle of wine in the Cavendish restaurant for under £30.