Temperatures have reached 40C for the first time on record in the UK, with 40.2C provisionally recorded at London Heathrow, the Met Office said.

The threshold was hit at 12.50pm as much of the UK sweltered in a heatwave, with parts of Wales and England under a red warning for extreme heat, posing a danger to life, pressure on the NHS and disruption across transport networks.

The extreme heat is fuelled by climate change, which is making every heatwave more intense, frequent and likely, scientists warn.

The new high for daytime temperatures comes after the UK experienced its warmest night on record on Monday, with temperatures remaining in the mid-20s.

The Met Office warned temperatures were still climbing early on Tuesday afternoon.

Yesterday, the air temperature record in Wales was broken twice within a couple of hours.

A highest-ever temperature of 35.3C was recorded in Gogerddan, near Aberystwyth, in the early afternoon.

Shortly afterwards, that figure was topped in Hawarden, a small village near the English border, which recorded a provisional air temperature of 37.1C.

Additional reporting: Rebecca Wilks