Runners are heading for the start line in an event which is being billed by organisers as “an important step in the return of mass participation sporting events”.

Runners and spectators who are taking part in the Reunion 5K at Kempton Park, Surrey, on Saturday will help to provide scientific data on Covid-19 transmission levels.

They will be involved in a socially-distanced or a non-socially distanced 5K run.

It is the only running event in the Government’s Events Research Programme, which is helping to test and build plans for the safe return of mass participation sport and events.

Everyone who attends has to provide evidence of a negative Covid-19 lateral flow test.

They will also be asked to take a PCR test both on Saturday and then five days later.

Approximately 1,000 socially-distanced runners will set off at regular intervals in the first group of races. They will be watched by a socially-distanced crowd of spectators.

Then approximately 1,000 runners who are not socially distanced will begin their 5K. Their spectators will also not be required to keep apart.

Organiser Hugh Brasher, the event director of London Marathon Events, described the event as “such an important step towards the return of large mass participation events in towns and cities across the UK”.

He said he had spotted that people have been cautious about entering an event which enables them to run in close proximity to each other for the first time in 15 months.

He said: “With hindsight, this is entirely understandable when social distancing has been our way of life since lockdown began.

“Research is now showing that the risk of transmission of Covid-19 outdoors is extremely low and we all know how important exercise and these mass events are to mental and physical health and to inspiring people to change their behaviour and adopt a healthier lifestyle.”

Mr Brasher is hoping it will help see the return of all kinds of running events – ranging from parkruns, the Great North Run or the London Marathon – to the sporting calendar.

Sports Minister Nigel Huddlestone said the Reunion 5k could help provide “essential data on the safe return of mass participation events”.

He added: “It’s fantastic to see so many runners and spectators getting involved in this event which will feed into policy decisions ahead of step 4 of the road map and hopefully see things like the great London Marathon return with crowds.”