Newly declassified files have revealed Dover would have been the Nazis' main starting point for an invasion - if they’d won the Battle of Britain.

The secret wartime documents - released today by the National Archives - show details of Operation Sea Lion as told by a German spy after the war.

According to Corporal Werner Janowski, storm troopers would have overrun the port and used it to ferry over enemy troops to invade Britain.

Adolf Hitler abandoned the plan after losing the Battle of Britain because his invasion force wouldn't have air protection.

But Cpl Janowski, who worked for the German Intelligence Service, the Abwehr, said if it had gone ahead Dover would have been bombed from the air before it was stormed by Germans.

Then he told MI5 interrogators: "Having effected a landing they would proceed along the cliffs to a point outside Dover where there were steps leading down to the beach and from this point they were to continue along the beach.

"They would regain the cliff head by means of some steps near Dover station and then pass alongside the railway station and take possession of three docks on which were gun emplacements.

"They would then signal to Luftwaffe that the docks were in their possession."

Dr Edward Hampshire, the principal records specialist at the National Archives, said: "Corporal Werner Janowski would have been one of the leading shock troops.

"They would have quite probably have worn Allied uniforms - they would have been disguised as British soldiers landed under the cover of darkness.

"His unit would have landed at a point outside Dover where there were steps leading down to the beach and they would have continued along the beach to regain the cliff head by means of some steps by the railway station.

"They then planned to pass along side the railway station and take possession of three docks.

"Dover was the closest major port to the European mainland. If you’re going to invade by barge because they are unpowered you need your port to be very close indeed.

"To some extent throughout Dover's history its been on the frontline in terms of English and British defence and this was definitely the case in the Wecond World War."