The code-breaking cogs helped decipher German messages

A set of cogs from the Second World War Enigma code-breaking machine has been discovered after languishing in a cupboard for up to 30 years.

The three rotors were found at the Royal Navy training establishment HMS Collingwood in Fareham, Hampshire, in a cupboard used to store flags and other equipment.

At first Chief Petty Officer Craig "Blood" Read and Petty Officer Dan Powditch thought they were imitations and put them back into the store in the old HMS Mercury building only to re-examine them several weeks later.

It is now believed the items were spares for an Enigma machine which used to be kept at the centre and which was donated to the National Museum of the Royal Navy (NMRN) at Portsmouth in 1983.

Now the box of three rotors is to be reunited with the machine when they are donated to the NMRN on Wednesday - the 71st anniversary of the Royal Navy's first capture of a fully functioning Enigma machine.

The Enigma machine donated to the NMRN in 1983 by HMS Mercury is a type M4 machine.

Richard Noyce, curator of artefacts at the NMRN, said: "The number M15653 on the machine matches the number on the box of rotors and the box is stamped with 'Kommando der Marine Sation Der 021' albeit smudged and difficult to read.

"With both items originating from HMS Mercury I think there can be no doubt the Enigma machine and its spare rotors were originally together.

"We are thrilled to be reuniting them again as they are a key part of our history."

The German military used the Enigma cipher machine during the Second World War to keep their communications secret.

It works using a series of rotating "wheels" or "rotors" to scramble plaintext messages into incoherent ciphertext with billions of combinations possible.

A NMRN spokesman said: "Breaking the Enigma ciphers gave the Allies a key advantage, which, according to historians, shortened the war by two years, thus saving many lives."