Ben Cottam puts on full waterproofs to cross the causeway to Sunderland Point, in search of the grave of a black slave.

There are 43 tidal islands around the UK, accessible just briefly each day along beguiling paths. Across the series, five writers journey across a favourite causeway to islands of refuge, pilgrimage, magic and glamour.

Wheels spin wildly and Ben peers anxiously through mud-sprayed windscreen as he tries to drive to Sunderland. There is no real boundary between land and sea, the coastline as fluid as the tide. The danger signs escalate and he remembers tales of insidious rising waters, drilled into him as a child by coastguards from Morecambe Bay.

He treks to what is uncomfortably called Sambo’s grave, the resting place of young black slave. Abandoned there by a sea captain in the 18th century, Ben wonders how his own family might have treated him and is heartened to find fresh tributes marking a lost life.

Producer: Sarah Bowen