London is baking in the hottest April day since 1949, triggering warnings for London Marathon runners amid predictions Sunday's race could be the warmest on record.
Temperatures soared to 29.1C in St James's Park making it the warmest April day for 69 years.
And the mercury could hit 23C in the capital on Sunday, prompting marathon organisers to add more water, ice and shower stations along the 26.2-mile route.
Conditions may be especially difficult for fancy-dress runners, including the almost 100 attempting Guinness World Records dressed in outfits like a suit of armour, a Paddington Bear costume and ski boots.
Regular runners are being advised to consider dropping their goal-times and run more slowly.
The hottest London marathon on record was 22.7C (72.9F) in 1996.