Boffins have come up with the perfect formula for decorating a Christmas tree.

(The research, commissioned by department store Debenhams, says that if you’re buying a 6ft Christmas tree, you will need an angel or star for the top that’s one tenth the size of the tree, and the number of lights required is found by multiplying the mathematical constant Pi (3.14) by the height of the tree in centimetres.

For example, a 183cm (6ft) tree needs 574cm of lights (183 x 3.14) or 18ft 9in. But perfection is only obtainable with 37 baubles and 920cm (30ft) of tinsel.

But how many chocolate Santas should I buy?)