Thousands start Dartmoor's Ten Tors challenge

The 56th event started at 07:00 BST, with 2,400 teenagers - many school and youth groups from across the South West - taking part

Thousands of teenagers are trekking across Dartmoor in the famous Ten Tors challenge.

Competitors aged 14 to 19 are hiking distances of up to 55 miles (89 km) visiting 10 nominated tors over two days.

The 56th event started at 07:00 BST, with 2,400 teenagers - many from school and youth groups from across the South West - taking part.

The first teams are expected to cross the finish line on Sunday morning.

The first teams are expected to cross the finish line on Sunday morning

Ten Tors

• The first Ten Tors expedition took place in September 1960

• Over the years interest in the challenge has grown and now up to 400 teams take part

• Camping overnight, the teams complete the challenge without adult guidance

• In 2013, the challenge saw its most significant overhaul in 30 years as Army bosses attempted to improve safety and reduce the number of river crossings

• During the challenge teams visit 10 nominated tors, which are hills or rocky peaks.

Source: BBC/Ten Tors

The canons marked the start of the Ten Tors challenge

The teenagers left Okehampton Camp, where Dartmoor National Park head ranger Rob Steemson said it was an "enormous challenge".

The event is organised by the Army and assisted by the Royal Navy, the Royal Air Force and the Dartmoor Rescue Group.

Each team has a GPS tracker, so safety teams can find out where each group of teenagers is. The tracker also has an emergency button if help is needed.