In 1994, HM Customs & Excise decided that since the introduction of VAT in 1973, they had been wrong to categorise Marks & Spencer's tea cakes as 'biscuits wholly covered in chocolate' (hence liable to the full rate of VAT) rather than 'cakes wholly covered in chocolate' (and thus zero-rated).
In 1995, M&S asked for repayment of all the VAT, £3.5m, they had been wrongly charged. The Commissioners said, no, you passed the cost onto the customers so we're only giving you the VAT on your profit: £350,000.
I wonder what the total in legal fees will be?
… and if you've got a receipt for M&S tea cakes between 1973 and 1994, I'd ask for a refund of the excess money you were charged.