Champions Hayley Yelling and Matt Smith head a top-class field of cross country runners at the national 4km championships in Stanmer Park tomorrow.

The 4km, or short course championships, incorporate the trials for the world cross country championships.

They are being held in conjunction with the All England Schools cross country championships.

Two thousand of England's top schools' athletes will be fighting it out for supremacy over six championship events.

It is the first time that both the boys' and girls' All England Championships have been held in Sussex. The boys' event was held in Stanmer Park in 1974, and it is also a first in Sussex for the national cross country championships.

Yelling, who is both the national and inter-county cross country champion, will lead the British team in the long course event at the world championships in Lausanne.

Charlotte Dale (Invicta Club, Kent) races in the women's event. She is the reigning national junior champion and also the European junior champion and will be heading the British junior squad in Lausanne.

All four men who have been selected for the long course race at the world championships, Smith, Spencer Barden (Belgrave), Rob Birchall (Birchfield) and Glynn Tromans (Coventry), the inter-county champion, are also among the entries.

Sussex will be represented in both races with reigning Sussex champion Stephen Rees-Jones (Brighton and Hove), runner-up Patrick Davoren (Phoenix) and bronze medalist Andrew Robinson (Horsham) in action. Ed Prickett (Crawley), who won last Saturday's Sussex League event at Bexhill, also races.

Sussex women's champion Caroline Hoyte (Arena 80), Julia Downes (Brighton and Hove), who won at Bexhill on Saturday, and Rachael Ogden (Worthing) race.

There are also international honours at stake in the junior (under-15) and intermediate (under- 17) races as the top eight will be selected to represent the English Schools team in an Home Countries international.

Start times: Senior men's trial: 12.35pm. Intermediate girls: 1pm. Iintermediate boys: 1.25pm. Junior girls: 1.55pm. Senior women's trial: 2.20pm. Junior boys: 2.45pm. Senior girls: 3.10pm; senior boys: 3.40pm.