From the eastern end of Portcressa Beach take the track along the shore.
After about 125m (135yds) turn left up the hill along what looks like a private drive; press on, however, and you will soon see the path heading off to the right.
Shortly after this, the path turns left and heads up some steep steps through the allotments, before turning right again and slowly descending to the sea shore.
The most direct route, however, is down the church path, and back up Old Town Road. Watch out for traffic here as St Mary's is nothing like as 'traffic free' as the guidebooks make out.
At the top of the hill, you can turn left on to Hospital Lane and return to Porthcressa via the Buzza Tower.