Mark Todd, Laura Bechtolsheimer and TV survival expert Bear Grylls will all join a 12-strong team of fundraisers today as they drive through Wiltshire and Gloucestershire.

Horses Help Heroes is attempting to drive 1,009 miles from Land’s End to John O’Groats in a replica World War I horse-drawn ambulance to raise money for injured servicemen.

The team, which includes eight amputees, some injured in action, set off from Cornwall on Tuesday (21 June) and is due to arrive in Caithness on Thursday, 29 June having driven day and night for nine days. Nine pairs of horses will be used.

The endeavour, is organised by paramedic Jacks El Tawil.

She said: “We have had a lot of bad luck so far but are back on track. Two of the five [horse and equipment] lorries had blow outs on the way down, we have had driving rain and the brakes got stuck on the ambulance after just seven and a half miles.

“Now my mare has rolled in nettles and has had a massive reaction and we are waiting for the vet to come and give her an antihistamine.”

The fundraiser is supported by numerous high profile figures, including Prince William, showjumper Michael Whitaker and dressage rider Carl Hester.

“Mark Todd will join us as we ride through Cirencester today,” said Jacks. “Bear will come to Chippenham and Laura to Malmesbury.”

They hope to raise £1m for Help for ABF The Soldiers Charity, Blesma and Combat Stress.

To follow the drive and donate, go to www.horseshelpheroes.org.uk.