The Hillingdon Duathlons are most probably the longest running triathlon series in the country. The first three were held in 1987 and there have been three every year since.
Originally they were run as an evening series, but changed to Sunday mornings, mainly because more competitors were finding it difficult to get to the event on time.
As the event became more popular, drafting became a problem. The hilly cycle was not breaking packs up, and the swim was too short to spread competitors out. In order to overcome this it was decided to do the run as the second discipline, this gives more time to spread competitors out. It gives the event a different feel to other triathlons.
Run of 6k, most of which is on road. The cycle is a 2 lap hilly course and measures 25km in total.