Secrets of the SAS revealed to mark the regiment's 70th anniversary

The Top Secret order authorising the first-ever Special Air Service (SAS) operation will be revealed today as part of a diary hidden away by the regiment for more than six decades.

It is included in a giant scrapbook, the SAS War Diary 1941-1945, containing orders, photographs, personal recollections, hand-drawn maps and newspaper cuttings, that is being released publicly to mark the regiment's 70th anniversary.

The order to the founder of the SAS, Captain David Stirling, begins: "Your force will consist of 54 men from 'L' Sec 1 S.A.S Bde. Your primary task is to raid both aerodromes... destroying as many aircraft as possible."

Military historian Gordon Stevens, one of the few people to interview the late Colonel Stirling, said: "So few people knew about the diary. Even within the regiment only a handful of people even knew it existed."

Mr Stevens, with publisher Martin Morgan, convinced the SAS Regimental Association to release the book.

"I was making a film about the SAS, during which I heard about this diary," explained Mr Morgan. "It was six months before I got to see it and six seconds to decide it should be published. It was another six months before I could persuade the regimental association it was a good idea."

The original diary was contained in a giant, leather-bound scrapbook that had been "liberated" from the Nazis. With many pages still blank, the historians added other unseen documents from the regiment and scanned them all to create 5,000, limited edition copies. As faithful as possible to the original, the copies are bound in leather with brass fixings and the pages have been scanned on to heavy paper to replicate the yellowing originals, making the 600-page book a 30lb tome. The only change has been that – apart from a limited 500 given to former SAS members – the Nazi logos on the German bindings have not been replicated.

Inside is an amazing insight into the birth of the SAS – as well as the origins of the Special Boat Squadron (SBS). Interspersed between tales of daring are original typed lists of soldiers killed, injured or captured, giving an unembellished account of their losses. Other lists include the names of men who would go on to become military legends, such as Lt (later Lt Col) Robert "Paddy" Mayne.

The account of the first operation in November 1941, when Stirling was determined to parachute in despite all odds, describes how it ended in disaster with only a third of the men making it out alive, beaten not by the enemy but by the desert. Without faltering, small groups went on to complete three more raids, destroying 88 German and Italian planes.

"The problem we had making it was that everyone who worked on it – graphic artists, printers and hand collators – stopped work and started reading," said Mr Morgan.

"We have had tremendous support and access from the regimental association in order to make this the most complete history we possibly could."

At a time when the regiment has suffered casualties in Iraq and Afghanistan, the books are to be sold to benefit its welfare fund. The war diary copies will be sold for £975, with 550 special editions, signed by original soldiers as well as recent Victoria Cross recipients, at up to £2,500.