Lydie Banot, 41, said she would release the rodents in the store's famous food hall, spread poison in its restaurants and place fleas in the clothes department, unless she was paid millions of pounds.
She had formed a grudge against the Knightsbridge store after receiving electrolysis treatment to remove facial hair at the store which she claimed left her face scarred, the Old Bailey was told. She was said to have become embittered after the initial failure of a sex-change operation in 1993.
The court was told that Banot - born Mario Kerr - began her blackmail attempt in November last year by sending a note to Harrods' owner, Mohamed al-Fayed, asking for pounds 5m to be placed in a Swiss bank account. It was followed by two further demands for pounds 2m each.
The police, who were brought in to run an undercover operation, at first thought they were dealing with a sophisticated blackmail campaign. A series of telephone calls and meetings were set up after she claimed she was being used as a go-between for an underworld team made up of former police officers, Customs and Excise officers and former soldiers who were blackmailing stores across the country. During negotiations, Banot reduced her demand for pounds 5m to pounds 50,000.
The plot was foiled and Banot arrested after a friend, Richard Killen, 47, told the security officer that she was acting on her own. Mr Killen was later charged with two offences of blackmail but these were dropped in court yesterday.
Banot, of Walthamstow, east London, pleaded guilty to three charges of blackmail.
Shani Barnes, for the defence, said the blackmail attempt had been "a cry for help" She was suffering from a rare condition called gender identity disorder and had no intention of carrying out the threats.
Passing sentence, Judge Charles Forrester said: "You made a sustained and sophisticated attempt to obtain money from Harrods.
"It must not be forgotten that Harrods was not to know who was behind this."
After the case, Mr Killen, of Finsbury Park, north London, said: "This woman needs help not punishment. When I knew what was going on, I contacted Harrods and told them there was no plot and she had mental problems. For my trouble, I was thrown in prison for eight weeks and missed Christmas with my children."Reuse content