Guardian Camera Club: Ralph Blackbourn on capturing achievement on film assignment

Registering. Parkrun relies solely on its volunteers to organise the events at a local level. A run the size of Bushy requires around 20 volunteers each week to keep it going, including people to zap the barcodes which tally up the times with the positions Photograph: Ralph Blackbourn/Flickr

Ready for the off. Every Saturday at 9am runners of all abilities gather in Bushy Park in Teddington, London for a free timed 5km run. The run began in 2004 with 13 runners, the event has increased to the point where 800 - 1000 runners turn out each week to run the course. So successful has the concept been there are now nearly 100 other "parkruns" throughout the UK and as far afield as Iceland, Poland and Australia Photograph: Ralph Blackbourn/Flickr

Sea of Runners. The tree is an oasis of calm signifying where the run starts. With 1,000 runners it can now take several seconds to clear the start line Photograph: Ralph Blackbourn/Flickr

Sprint Finish Photograph: Ralph Blackbourn/Flickr

Finish Line. The great thing about parkrun is you can run it in 16 minutes or 60 minutes and no-one minds Photograph: Ralph Blackbourn/Flickr

Finish Tokens Photograph: Ralph Blackbourn/Flickr