Lizzy Hawker celebrates her 2010 women's victory in the Ultra-Trail du Mont Blanc. Photo: Damiano Levati/The North Face

Two of Britain’s top mountain athletes are gearing up to defend their titles in one of the world’s toughest races.

Jez Bragg and Lizzy Hawker will both head to Chamonix to attempt a repeat of their victories in last year’s Ultra-Trail du Mont Blanc.

The race was truncated last year due to severe weather, but Dorset-based Bragg headed the men’s field and Hawker, who lived in Cheshire but now spends much of the year in the Alps, won the women’s race.

The North Face ultrarunners will start the 166km (103-mile) circuit around western Europe’s highest peak in a field of 2,300 of the world’s best mountain runners following the walking route that normally takes a week but which will be covered by the fastest competitors in about 21 hours.

The main race starts on 26 August, with Bragg facing stiff competition from fellow The North Face team member, American Mike Wolfe, who was second last year. Hawker already holds a record, having won the women’s race three times, in 2005, 2008 and 2010.

The North Face Ultra-Trail Du Mont-Blanc will be run for the ninth time and the event takes place between August 22 and 28 in the French Alpine resort of Chamonix.

A total of 5,500 competitors from 58 different countries will take part in one of four races: The North Face UTMB; the Courmayeur Champex Chamonix up to 98km; the Sur les Traces des Ducs de Savoie covering 110km; and the La Petite Trotte à Léon which, at a non-stop 300km is probably the most misnamed.

The Ultra Trail crosses nine high altitude mountain passes, with a total positive height gain of 9,500m, circling the Mont Blanc massif through three countries: France, Italy and Switzerland.