The elderly woman exposed as the longest-serving Soviet spy in Britain was a fresh-faced 25-year-old when her political idealism first drove her into spying for the Soviet Union.

Melita Norwood was the daughter of a Latvian father and English mother, and had a sister and half-brother.

For decades her suburban neighbours suspected nothing

Like her father, she has always held fiercely left-wing views.

Her spying career began four years after Joseph Stalin had seized power, long before his atrocities had become known to the outside world.

But for the 40 years that she worked for Moscow, her bank balance rarely reflected the spoils of her labour. She says she was working for the ideology not the financial reward.

The great-grandmother of 87 still lives in the same, spartan south London house which she bought with her husband, a maths teacher, 50 years ago.

Two citations to her late husband, Hilary, for his work in the trade union movement as a member of the National Union of Teachers, are proudly displayed.

They had been married for 50 years when he died in 1986. He too was a member of the Communist Party. She says he disapproved of her spying, but "never tried to stop me".

Unremarkable but intelligent

She had been working for five years in the general office of the British Non Ferrous Metals Research Association in Euston, North London when her career in espionage first began.

Her 40-year treachery brought few financial benefits

The association was working on the top secret business of developing Britain's nuclear deterrent.

By the time she agreed to work for the KGB, she had been promoted and was personal assistant to the director.

As a highly trusted employee, sensitive documents crossed her desk each day.

But the unremarkable but highly intelligent office worker would pass those secrets to Moscow via clandestine meetings with Russian agents.

'I am not a spy'

Still, she refuses to discuss the actual passing over of documents and refuses to say who wooed her to the KGB.

The last time she visited Russia was in 1979, with her husband, when she says she again rejected financial reward.

She has one daughter who works in a school laboratory, two grandchildren and a great-grandchild.