More than 1,000 runners took part in the Watford 10k race on bank holiday Monday.
Hundreds of children also battled through the heat in the 1k and 3k fun runs in Cassiobury Park.
Race organiser Liz Hizli, community fundraiser with Watford Mencap, said it was a "glorious day" but that the course was harder than ever with the athletes having to face more hills than in previous years.
She said: "Over 1,000 runners took part in this year’s Watford 10k on what turned out to be a glorious day.
"There were also over 400 children in the 1k - the most we've ever had - and nearly 100 in the 3k run.
"The ever popular charity event was back into the woods where the beautiful bluebells could be appreciated, although the runners did have a few more hills to contend with than in previous years."
The 1K race
Nigel Rackham stormed home with the win in the 10k in 35 minutes 31 seconds.
In second place was Pawel Grygo who completed the event in a time of 36 minutes 35 seconds and in third place was Mike Dooley who finished the run in 37 minutes and 22 seconds.
The first woman to reach the finish line was Caroline Whittaker with a time of 42 minutes 40 seconds, placing 30th overall.
The winner of the 3k fun run was Euan Wiley in a time of 10 minutes seven seconds, pipping runner up Will Brown by eight seconds and third place Matthew Chadwick by 13 seconds.
The event has consistently raised more than £16,000 for charity. This year's total is still being totted up but Liz said they were on track to raise a record £20,000.
Liz continued: "This has become such a regular event on runners' calendars that sometimes the fact that it is for two very worthwhile local causes is forgotten and it is a struggle to get participants to raise money.
"The entry costs just go towards the running costs and that is why Watford Mencap and Watford Round Table urge everyone to try and raise at least £25.
"This will then get them into a draw for a Harry Potter Experience Family ticket which is worth at least £85.00 - worth a chance.
"It's not too late to encourage friends and family to help by setting up a just giving page."
Watford & District Mencap provides a range of services for adults and children with learning disabilities, their families and carers, in the South West Herts region.