- Turn right out of the car park in Worth Matravers to head down through the village, turning right on the road ahead and then left at the village pond.
- Ignore the first footpath on your left, just after the junction, but take the second a short distance beyond (marked 'no through road') and follow it out onto the heathland, heading due south with it towards the sea. Carry on alongside the stream in the Winspit Bottom, ignoring the footpath on your right that heads back into the village, as well as the smaller paths lower down the valley, until you come to the South West Coast Path.
The curious-looking ridges on the hillsides around Winspit date back to medieval times. Called strip lynchets, they were carved into hillsides to provide more arable land for farming.
Winspit Quarry was a major source of Purbeck limestone until the 1940s when it was used instead as a site for naval and air defences during the Second World War. The dramatic caves in the quarry were opened to the public after the war, although many have since been closed, in some cases for safety reasons and in other cases because they are home to a colony of greater horseshoe bats, the UK's largest bat, currently in danger of extinction. Fans of the 1970s TV series Blake's 7 may recognise the quarry as the planet Mecron II, although Dr Who fans will argue that it is the planet Skaro from Destiny of the Daleks.
- Turn right onto the Coast Path, following it out around the headland to the National Coastwatch Institution lookout station, which is open to visitors unless there is an emergency. Take the path to the right for a detour to St Aldhelm's Chapel.
The monument on the tip of the headland was designed by local councillor and sculptor Tony Viney to commemorate the importance of the peninsula in the wartime development of radar. It consists of two radar dishes cunningly arranged to symbolise a large fire basket, linking the modern warning systems with the fire beacons used to warn of the approaching Armada in 1588 (see below).
St Aldhelm's Chapel dates back to the thirteenth century and was built on the site of a much earlier Christian hermitage, but the current building is a nineteenth-century restoration. As well as being noted for its square shape, the chapel is unusually aligned, with its corners - and not its walls - facing the four compass points (see the St Aldhelm's Chapel Walk). St Aldhelm was Abbot of Malmesbury and Bishop of Sherborne at the end of the seventh century and was a noted Latin poet and ecclesiastical writer.
The present lookout, overlooking the notorious St Alban's Race, was built in the 1970s for the Coastguard Service but was returned to the Encombe Estate when the service stopped visual lookout duties in 1994. It is one of 49 NCI lookouts set up the same year around the coastline of England and Wales after two fishermen died on the Lizard within sight of the newly-closed coastguard lookout. On St Aldhelm's Head, the NCI leases the building at a modest rent of 'one crab per annum if demanded'.
- Returning to the Coast Path from St Aldhelm's Chapel turn right to carry on around the headland. The path travels along the edge of a high flat plateau as it heads inland above the eastern shores of the scooped-out bay of Chapman's Pool.
From here there are dramatic views along the coastline looking west, with a series of scarred white cliffs rising vertically from the thick vegetation growing in the slumped undercliffs. The rock around the bowl of Chapman's Pool is Kimmeridge Clay Shale, a versatile rock which has been exploited for its many manufacturing uses since the Iron Age. Like other local limestones, it is also full of fossils. The cliffs above, however, are Portland limestone, laid down on top of the shale in a later period, before erosion and other processes reshaped the local landscape.
- Very soon steps descend into a steep-sided valley, and a footpath heads off to the right. Ignore this side path and carry on up the steps out of the valley and along the path above Chapman's Pool.
- A number of tiny paths travel over the undercliffs on your right. After you have passed the end of Chapman's Pool a slightly bigger path zigzags up the hillside from the boathouse, crossing the Coast Path to continue inland. Carry on past this path, staying on the Coast Path as it veers right and then drops steeply down into the valley below.
Renscombe Down, on the ground to the east of Chapman's Pool, was the nerve centre of the UK's radar development during the Second World War. Scientists began working on radar in 1935, originally operating on the Suffolk coast and then moving to Dundee before relocating here, choosing this location because the high flat terrain was ideal for radar and the site was further from any potential invasion by the Germans. In May 1940, about 200 people arrived in Worth Matravers to work on the radar systems, which included developing the rotating aerial and map display used for tracking the target. After this, the main objectives were to develop systems with a longer range, and for use in aircraft navigation.
In February 1942, British paratroopers raided a German radar installation on the French coast, bringing back key components, and the British government feared that the Germans might raid Worth Matravers. In May of that year, the whole operation was relocated to Malvern, in Worcestershire. By this time there were 2000 personnel working on Renscombe Down.
During the same period, St Aldhelm's Head was one 21 coastal Early Warning RDF (Radio Direction Finding) stations around the British east coast, from Orkney in the north to Weymouth in the south. There were two 240ft masts near the village and a further site on the clifftop to detect low-flying aircraft. Operations continued here after the radar scientists had left and were used by the RAF as a training station after the war.
There were other radio and radar stations in and around Purbeck, including an Oboe radio navigation station, codenamed Tilly Whim, at Durlston; a Coastal Defence (CD) on Swanage Down for detecting ships; and VHF radio communications masts, for communicating with aircraft, on Nine Barrow Down. This last was particularly important after the D-Day landings when the planned undersea telephone cable link was damaged.
- Leave the Coast Path when it starts to head back out towards the sea, instead take the path to the right towards Worth Matravers. For a shorter walk carry on along this path to return to the village; but otherwise continue along Hill Bottom to the next footpath towards Worth Matravers, heading to your right below the quarries.
These are the Swanworth Quarries, another source of Purbeck limestone. They are of particular interest to geologists, containing the most complete section on the Isle of Purbeck of the many different beds of limestones. Local limestone beds are also a source of fascination to palaeontologists, or fossil-hunters, and they are famous for their fossilised dinosaur footprints. These are mostly from mammals and small dinosaurs, but at nearby Keat's Quarry, diplodocus footprints were discovered that are almost a metre across.
- Turn right onto this path and follow it back to Worth Matravers, turning left on the road beyond the church to return to the car park at the start of the walk.