Grid reference: Car Park SP731 332; Coombs Quarry SP 733 327.

Ordnance Survey map: Aylesbury and Leighton Buzzard Sheet 165.

Geological maps: 1:50,000 series Thame sheet 237 and Aylesbury sheet 238.

Car parking and picnic facilities are available at Coombs car park, off the Coombs to Adstock Road, near Thornborough, Buckinghamshire.

To reach Coombs, take the A421 from Milton Keynes or Buckingham or the A413 from Aylesbury or Buckingham and Thornborough Road runs between both A roads connecting the villages of Thornborough and Padbury