Dermot O’Leary uncovers the story of the RNLI’s heroic efforts in the Second World War, as its crews were called to serve in the most perilous of conditions, saving 6,376 lives.

In Dungeness, the crew are called out to reports of a small boat in the middle of the shipping lanes, and they discover that the casualty is the subject of a major manhunt.

In Porthcawl, a fisherman has been dragged lifeless out of the sea by bystanders. The lifeboat crew race to the beach and join the desperate attempts to resuscitate him.

In Castletownbere, crew member Donagh faces a baptism of fire on his first ever shout as the crew carry out a dramatic rescue of a fisherman who’s suffered a suspected stroke.

In Queensferry, on the east coast of Scotland, an American visitor is caught out by the tide and is barely conscious when the RNLI crew drag him out of the water.

In Humber, the crew must work closely together to pull off the dangerous medivac of a fisherman with a spinal injury.

In Walmer, the crew respond to reports of a major incident involving a small boat in the Channel. On arrival, they are faced with mass casualties in the freezing water.

In Mudeford, on the Dorset coast, a search for a missing kayaker quickly escalates when it emerges that there are six more kayaks unaccounted for.

In Porthcawl, on the south-west coast of Wales, the crew receive a call about a swimmer who’s been swept out to sea in a rip current - as his wife and son watch on helplessly.