The Foreign Secretary and Deputy Prime Minister will join the Duke of Edinburgh, who is representing the King, at the event on Sunday.

Brockwell Park in south London is due to host several festivals, including pop event Mighty Hoopla, between May and June.

As of Friday, 80.6mm of rain has been recorded for the UK this spring, nearly 20mm less than the record low for the full season of 100.7mm in 1852.