A 95-year-old veteran brought Dame Kristin Scott Thomas to tears when he handed the actress an Arctic Star medal for her grandfather. Here John Roberts, from Whitstable, tells Brad Harper about the perilous convoys to Russia during the Second World War...

Every night when 19-year-old John Roberts clambered into his bunk aboard HMS Serapis, the sound of water lapping against the side of the ship filled his mind with terror.

"One had to think a torpedo might suddenly come through the side," he says.

The destroyer was part of an Arctic convoy, escorting merchant ships carrying vital supplies to keep Russia in the Second World War.

It was a perilous journey in freezing temperatures across the Norwegian Sea - with mines and Nazi submarines an ever-present threat.

And one fatal night in February 1944, a German torpedo hit another of the warships in the convoy.

The teenager watched in horror as just 100 yards away the ship was sunk. About 220 people died and only 12 escaped the wreckage alive.

Mr Roberts, now aged 95 and living in Tankerton, recalls: "You didn’t last for more than five minutes in the water.

"On that particular night, I remember the sea was quite rough and choppy. But when you got into your bunk - and my bunk was on the side of the ship and you could hear the water lapping - one had to think a torpedo might suddenly come through the side.

"My captain had been on the bridge of the ship for four hours and he could hardly move.

"He had a coating of about two inches of ice all over his body. He had to have two sailors pick him up from a chair on the bridge, take him to the hatch, lower him down and carry him into his little sea cabin where he thawed out.

"I think the Russian convoys - if you stopped and thought about it - they were scary. The weather was terrible; you had very powerful gales, the sea was huge and a destroyer is quite a small ship."

Mr Roberts describes how one man aboard a merchant ship was found to have ice in his stomach, which doctors treated by pouring lukewarm water down his throat to melt it.

Due to gangrene the man later had to have his legs sawn off - with no anaesthetic.

Alongside fellow veterans, Mr Roberts has campaigned for greater recognition of those who took part in the convoys, which culminated in the issuing of the Arctic Star medal in 2012.

And tonight he is appearing on a Channel 4 documentary with Dame Kristin Scott Thomas, in which the actress explores her grandfather's role during the war.

She learns how William Scott Thomas helped to rescue thousands of allied troops from Dunkirk and later captained a destroyer on the convoys.

At one point the Four Weddings and a Funeral star is brought to tears as Mr Roberts hands her an Arctic Star with her grandfather's name on.

In total, Mr Roberts helped escort four convoys to Murmansk, Russia.

After service on the aircraft carrier HMS Triumph in the Mediterranean, he become a qualified military flying instructor. He later served with the Australian navy at the end of the Korean War.

In 1963, he was promoted to Captain and was given command of various ships - the most impressive being the 804ft aircraft carrier HMS Ark Royal.

He later rose to Rear Admiral and was appointed a Companion of the Order of the Bath in the 1976 New Year Honours List. He retired in 1978.

The grandfather-of-five now tells his remarkable tales to school children across Kent who sit and listen in awe to the brave hero.

He moved to Tankerton five years ago, where he lives with wife Gillian.

• My Grandparents' War will air on Channel 4 at 9pm tonight.

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