Gallery: It’s hotter than Ibiza - but not for much longer

Visitors look at the fountains in Alnwick Garden in Northumberland

Ice cream sellers have said the recent heatwave has sent sales soaring, with some vendors saying they have enjoyed the best April for sales in more than a decade.

But the weather is then set to take a turn for the worse, with rain, cloud and cooler temperatures predicted for the second half of the week.

And showers could hit the capital this Sunday as tens of thousands of runners take part in the London Marathon.

The sun balances next to St Albans Church in Earsdon, North Tyneside

Dan Williams, a spokesman for the Met Office, said most of Britain will enjoy good weather until Wednesday.

He said today will be “a good day for England and Wales with lots of blue skies and sunshine”.

The mercury is expected to hit 18C (64F) in London which is higher than average for this time of year.

Mr Williams added: “Wednesday again is a decent day, there is a bit more cloud around along the eastern side of the country and up in Scotland but there will still be good sunny spells in the south and western parts of the UK, in Wales and the Midlands.”

But he warned that things will cool slightly on Thursday and showers are expected to hit Britain at the end of the week.

Mr Williams said: “By Thursday a lot more cloud will be around in general and there will be light rain over Scotland.

“For most it will be a dry day still with some sunny spells, but generally that cloud is the herald of slightly more unsettled weather.

“The high pressure that has been dominating for the past few days moves over and we see a bit more of what you would expect this time of year.”

People sitting on a bench enjoying the hot weather, on the South Bank in central London.

Patchy rain and breezier conditions are expected to hit at the weekend, and could bring unsettled conditions as runners line up for the London Marathon.

Ice cream vendor Katy Alston, 47, known as Mrs Whippy to her customers in the Sussex towns of Bognor Regis and Chichester, said the good weather has sent ice cream sales through the roof.

She said: “We have had a nice warm April and it has been absolutely amazing for sales.

“In April we usually potter around and find our feet, but this year it has been really busy. We did an event last week at Chichester University and sold out of ice creams in 40 minutes. It was just incredible - and it’s down to the weather.”

She added: “We have had our best April ever and I have been in business for 11 years. I would say our turnover for April has trebled.”