Snowdon Race runners. Photo: Denis Egan

Entries for one of Britain’s biggest mountain races open on Thursday and organisers are expecting a scramble for places.

St David’s Day is the appropriate day for top runners to register for the International Snowdon Race, the 16km race up and down Wales’s highest peak.

Organisers warn any walkers, especially those organising charity treks, that the mountain will be busy on race day, 28 July, as runners tackle the 10-mile route from Llanberis to the top of the 1,085m (3,560ft) mountain before turning for the fast descent alongside the mountain railway.

This year’s race has been confirmed as a trial in the 2012 Skyrunner World Series where British and international athletes can gain points for the ranking based on the best of three main races and one trial.

Organiser Stephen Edwards said: “We have already had a huge amount of interest, with many emails and phone calls asking when and how people can enter this year’s event.

“Entries will be online via the Snowdon Race website on 1March – particularly important to us here in Wales as it is also St David’s Day.

“Last year we had a full field by the end of March, and we expect the limit to be reached even quicker this year.”

Any runner who has taken part in the event in the last five years can apply for the 200 places available from Thursday, and a further 400 places will be available from 17 March.

The race involves running from the edge of Lake Padarn in Llanberis to the highest summit in Wales and England and back down in one of Europe’s toughest endurance challenges.

The first ever race was held on 19 July 1976 after Ken Jones of Llanberis put forward the idea to the village’s carnival committee.

Eighty-six runners turned up for the race and it was won by Dave Francis from Bristol who completed the course in 1hr 12mins 5secs.

Mr Jones said: “It was pure curiosity that sparked the idea of the Snowdon race.

“As a walker and runner myself I’d always wondered what was the fastest time someone could run up and down Snowdon. So we arranged to hold the race as part of the annual carnival activities in Llanberis and the event has grown ever since.”

The men’s record now stands at 1hr 2mins 29secs, set in 1985. Fastest women’s time for the return trip is 1hr 12mins 48secs, with the fastest run to the summit 39mins 47secs.

Busiest parts of Snowdon on the July race day will be along the Llanberis path. Snowdonia National Park Authority will be working with organisers to publicise the event in advance, with signs to warn walkers of the upcoming challenge.