Four runners were rushed to hospital - at least one unconscious for 45 minutes - after they collapsed in scorching temperatures while taking part in the Richmond Park half marathon.

A number of local residents have questioned whether the RunThrough event should have been allowed to go ahead on Sunday in the high temperatures, which topped 30c on Sunday.

The Royal Parks Police issued a warning about exercising in the heatwave and wrote on Twitter: "Officers have been assisting the London Ambulance Service after four people were taken to hospital after collapsing during a running event in Richmond Park."

A number of Richmond residents, competitors and eye-witnesses took to social media to question the wisdom of allowing the event to go ahead.

One wrote: "Well done to the paramedics that arrived. Shocker by RunThrough UK to keep the race on.

"Poor chap we were with for an hour at the end collapsed and was unconscious for 45 minutes - he could've died today."

Thomas Davies, who took part, said: "I ran this event! Don't think it should have gone ahead! I hope everyone is okay. The heat was absolutely mad!

"Absolutely boiling weather! Don't mind entering the pain cave but that was rough."

Andrew Grant said: "Twelve emergency vehicles and an air ambulance. What a huge amount of public resources for an event which should have probably been postponed."

Paul Gray asked: "Will the organisers pick up the bill? …. Clearly this was ill thought out and clearly, safety was not thought through for the event in such hot weather.

Another local wrote: "Absolutely unbelievable that people were running a race around Richmond Park in this heat. Absolutely zero common sense."

Debbie Kellow wrote:

Seriously? Why did this even go ahead? The emergency services are already under enough pressure. Staggeringly stupid.

Debbie Kelly added: "Seriously? Why did this even go ahead? The emergency services are already under enough pressure. Staggeringly stupid."

Paul Gray said: "Clearly this was ill thought out and clearly, safety was not thought through for the event in such hot weather."

RunThrough UK has been contacted for a comment.