Patricia Ruff talks with her brother Jack Waterfall about the creation and writing of the book about the The Battle of the Heligoland Bight took place on 18 December 1939 and is now regarded as a turning point in the war following heavy losses for the Royal Air Force during the disastrous daylight raid.

Jack Waterfall, 75, from Ely, Cambridgeshire, who organised the event, had never heard of the battle until he was researching his uncle, who died while serving in the RAF in 1940.

The Heligoland Bight is an area near the German ports of Wilhelmshaven and Bremerhaven.

The Air Ministry decided to launch an attack on German ships there to prevent them from supporting U-boats in the North Atlantic.

On 18 December 1939, 24 Wellington bombers from RAF stations in Honington and Mildenhall in Suffolk and Feltwell in Norfolk were sent to sink or damage as many ships as possible.

The targets were strictly military ones only and civilian casualties had to be avoided. The only way to ensure accuracy was for the mission to take place in daylight.

There was a belief that bombers flying in close formation in daylight could defend themselves against fighter aircraft. That theory was about to be tested.

"The action was such a disaster for the RAF, with the loss of half of the 24 bombers sent and 57 airmen killed," said Mr Waterfall.

"In the spring of 1940, Bomber Command changed to night operations, which by many is regarded as a turning point in the war."

Mr Waterfall was unaware of the story until he teamed up with a cousin to find out what happened to their uncle, Sgt JH Waterfall, who went missing in action over Germany in 1940.

"With the help of German contacts we traced our uncle's grave and I was shown a really dramatic painting of Wellingtons being shot down, which turned out to be the Battle of Heligoland, which I had never heard of," he said.

"After seven years of research, we had tracked down most of the relatives of the men involved in the battle, and we published a book, Daylight to Darkness, and launched a website to mark the event."