Clocks go forward by one hour tonight as we switch to daylight saving time.

Summertime begins at 1am on Sunday morning.

It comes as a new US study reveals that losing an hour of sleep when the clocks change raises the risk of having a heart attack on Monday by 25 per cent.

The effect is reversed in Autumn - when the clocks go back an hour, the heart attack risk falls by 21 per cent.