I've found 10 walking tours

Tour	Price
Cycling Vietnam show more	13 nights £3045pp including flights	View
Members are eligible for cashback on this trip of up to £61pp

Borneo Wildlife Discoverer show more	14 nights £5299pp including flights	View
Members are eligible for cashback on this trip of up to £106pp

Classic Sicily show more	7 nights £2495pp including flights	View
Members are eligible for cashback on this trip of up to £50pp

Train to Machu Picchu show more	15 nights £3995pp including flights	View
Members are eligible for cashback on this trip of up to £80pp

The Heart of Ancient Greece show more	11 nights £2795pp including flights	View
Members are eligible for cashback on this trip of up to £56pp

Highlights of South Africa show more	13 nights £4795pp including flights	View
Members are eligible for cashback on this trip of up to £96pp

Uzbekistan: Heart of Central Asia show more	11 nights £2795pp including flights	View
Members are eligible for cashback on this trip of up to £56pp

The Wonders of Ancient Crete show more	7 nights £1945pp including flights	View
Members are eligible for cashback on this trip of up to £39pp

Ancient & Modern Japan show more	13 nights £6345pp including flights	View
Members are eligible for cashback on this trip of up to £127pp

Grand Tour of South America show more	17 nights £4995pp including flights	View
Members are eligible for cashback on this trip of up to £100pp