At 9am this Saturday around 500 hardy, some would say foolhardy, souls will gather near the Diana Fountain car park in Bushy Park to play their part in a milestone for a sporting phenomenon.

It is four years since the first Bushy Park 5km time trial was run – and it is fair to say that on the Times sportsdesk we have been keen to follow them every step of the way.

The first race, on Saturday, October 2, 2004, attracted 13 runners.

But perhaps the omens were good as, just like the first London Marathon in 1981, it finished in a virtual dead heat.

The record books show Chris Owens of Ranelagh Harriers as the first winner, although he recorded the same time – 18 minutes, 47 seconds – as Striders of Croydon’s Matt Morgan.

It is fair to say there was little sign of what was to follow seven days later when 14 people turned up. In those opening two weeks, every competitor was a member of a local running club.

Skip forward four years and the Bushy Park event has spawned nine other races in the UK (including one in Richmond Park) as well as one in Zimbabwe.

All operate under the Parkrun banner – you can see all the details for yourself at a lovingly produced website at parkrun.com The beauty of the time trials, which certainly caught the imagination of our sports desk from the early days, was that this was sport in its rawest and purest form.

Only made possible by volunteers, anyone can and does take part, literally by getting to the start in time to run (although, for logistical purposes, organisers ask that people who haven’t run before register 24 hours before).

We published the top 50 runners of last week’s Bushy Park time trial, which was won in a pretty sensational 16 minutes, 57 seconds by Stragglers’ Danny Norman.

As someone still to break the 25-minute barrier for a 5km run, I am in awe of the 48 runners who completed the event inside 20 minutes.

The talk on the finishing line isn’t really of who won, but of whether or not runners have beaten a new personal best.

Even for the 389th of the 391 runners who completed last week’s Bushy Park event there was a success story – Michelle Price had beaten her previous best time by 56 seconds.

There used to be a slogan ‘sport for all’. Happy birthday to an event that genuinely offers that.