Now return to the path and turn left down the steep slope. At the bottom of the slope, turn left going through the Castlefields gates. Continue straight along Patford Street. Cross at Cox’s Hill towards the Lansdowne Hotel. Then cross the A4 towards the library. Follow the river along Church St, then take the path on your left to a small seating area with mosaics.

Note the bronze head of Dr Joseph Priestley in the centre of the pavement. In 1774 he discovered oxygen at nearby Bowood House, where the Marquis of Lansdowne had set up a laboratory. Priestley carried out some experiments in his garden pond at the Old Vicarage, farther up the Marden from the plaque named Doctor's Pond. The mosaic tiles here illustrate the importance of oxygen to life on earth.