Dozens of people required medical assistance because of heat-related illness on the second day of Royal Ascot, racecourse officials have confirmed.
The event attracted over 41,000 spectators on Wednesday, during which temperatures reached 29.7C (85F).
A Royal Ascot spokesperson said one person was taken to hospital while a further 42 received treatment on site.
Free water is being provided to all those attending, the spokesperson added.
They also said additional gazebos and parasols had been installed.
Horses are kept cool using misting fans and a mobile water bowser with a 1,000-litre (220-gallon) capacity.
In total, more than 250,000 people are expected to attend the five-day event, which ends on Saturday.
The event was founded by Queen Anne in 1711 and is now well known as a key social occasion, as well as a sporting event.
King Charles, Queen Camilla and the Prince of Wales appeared in a carriage procession at the event on Wednesday – but the Princess of Wales was not in attendance.
Amber heat health alerts were issued across the whole of England from 09:00 BST on Thursday, with temperatures likely to exceed 30C for the first time this year.
The UK Health Security Agency said “significant impacts are likely” for health and social care services, including increased demand.
It follows a period of high temperatures across the UK with yellow heat health-alerts having previously been in place.
