The temperatures were experienced around the country with Scotland, Wales and Northern Ireland all experiencing their highest temperatures of the year.
Emma Boorman, a Met Office forecaster said: “It’s been the warmest day of the year with St James’ Park in London recording 27.1C. There was lots of lovely sunshine out there to enjoy. All four countries in the United Kingdom have recorded their highest temperatures of the year.”
In Scotland, the highest was in Kirkcudbrightshire which recorded 22.5C (72.5F), with Aberporth in Wales reaching 24.3C (75.7F) and Killowen in County Down, Northern Ireland, recording 18C (64F).
Bookmaker Coral is offering even money that 2016 is the hottest year on record in the UK after the firm saw a sustained gamble over the last 48 hours leading them to slash the odds from 3-1.
It is also offering just 2-1 that the record high of 32.8C (91F) is broken in May, while it is 6-4 for 30C (86F) to be recorded this month.
Spokesman John Hill said: “Punters are convinced we are set for the hottest year on record in the UK as we’ve seen a sustained gamble in the betting over the last few days.
“We may not have to wait long for 30C or higher to be recorded in 2016 as the odds suggest it is likely to arrive this month.”
Ladbrokes also said bets had been pouring in and it has been offering 2/1 for the mercury to reach 30C or higher before the weekend is out.
Jessica Bridge of Ladbrokes said: “It’s getting hotter by the day and punters are convinced the sunshine’s here to stay all summer.”
However, the heatwave is not expected to last. Today will be cooler, with a fresh easterly breeze developing.
Tuesday and Wednesday will be cloudy and cooler still, with outbreaks of rain, heavy and thundery at times.
Thursday will be drier but will stay cloudy and cool with a few outbreaks of rain.
Any mist patches will soon clear with all parts seeing another dry day with mostly unbroken sunshine. Warm again inland, but the easterly breeze keeping it cooler near the coast. Maximum Temperature 21 °C.
Staying mostly dry this evening and overnight but increasingly cloudy across the region, perhaps with the odd shower in the south by morning. Minimum Temperature 9 °C.
Some sunny intervals but cloudier than Monday with a few showers, perhaps heavy in the south by evening. A little cooler than of late, with the easterly breeze persisting. Maximum Temperature 18 °C.
Outlook for Wednesday to Friday:
Wednesday cloudy with some showery rain, perhaps heavy in places. Bright or sunny intervals and the odd shower Thursday and Friday, and much cooler by Friday as winds turn northerly.