Police are to mount a major security operation at the funeral of Lady Thatcher at St Paul's Cathedral next Wednesday amid growing fears about the threat posed by dissident Irish republican terrorists and far left groups.

As Buckingham Palace said the Queen would break with recent precedent to attend the funeral with the Duke of Edinburgh, Scotland Yard confirmed initial planning for the policing operation. Commander David Martin, head of the Met's public order unit, who has a counter-terrorism background, will be in charge.

The late prime minister, who was targeted by the IRA in the 1984 Brighton bombing in retaliation for the hardline stance she took in the 1981 hunger strikes, lost two close political allies in republican terrorist attacks.

A number of world leaders are expected to attend the "ceremonial funeral", which will fall short of a full state funeral on the wishes of Thatcher. It is understood that the late prime minister felt uncomfortable about lying in state before such a funeral and feared that a parliamentary vote, which would have to be held to approve public funds, could be divisive.

Invitations are yet to be formally issued, and because it is not a state funeral, countries are not automatically expected to send heads of state or their representatives. But FW de Klerk, the last president of apartheid South Africa, who was embraced by Thatcher as a reformer, became the first former head of state to confirm his attendance. De Klerk, who ordered the release of Nelson Mandela from prison and then agreed to the negotiations that ended apartheid, will attend with his wife, Elita.

David Cameron will lead the tributes to Thatcher on Wednesday when parliament is recalled from its Easter recess for MPs from across the political spectrum to pay their respects to her. The House of Lords is also being recalled.

Ed Miliband, who has instructed his MPs to follow his lead in showing respect for Thatcher, suffered a blow when one of Labour's longest serving MPs said MPs should be free to criticise the "brutal contempt" with which Thatcher treated millions of working people. David Winnick, who was first elected to parliament in 1966, said it would be "absolutely hypocritical" if parliament did not hear all sides of the late prime minister's legacy.

Years of planning for the funeral were put into action on Tuesday when Francis Maude, the Cabinet Office minister, whose late father, Angus, served in Thatcher's first cabinet, chaired a meeting of the True Blue operation. Maude briefed the prime minister about the preparations at the daily 8.30am Downing Street meeting.

A friend of the Thatcher family attended the meeting about the funeral, which is being carefully organised to respect the wishes of Thatcher. It is understood that the government will advise the family about the guest list. Her children, Sir Mark Thatcher and Carol, will have the final say.

It will be the first time the Queen has attended the funeral service of a former prime minister since Sir Winston Churchill's state ceremony in 1965. Palace officials described it as a "unique" occasion.

The body of Britain's first female prime minister was moved by private ambulance in the early hours of Tuesday from the Ritz hotel suite where, according to friends, she died at 11.28am on Monday after suffering a stroke while sitting in bed reading a book.

The police will mount a large operation as they take account of a series of challenges ranging from dissident Irish republican terrorists to activists on the far left who may use the funeral to show their contempt for Thatcher.

Police were called to a number of incidents in London and Glasgow on Monday night after a series of "parties" were held to "celebrate" the death of Thatcher. Chuka Umunna, the Labour MP for Streatham, made clear his anger on Twitter after a "party" was held in the Windrush Square area of Brixton in his constituency.

Umunna tweeted: "Holding a party to celebrate the death of any person is totally wrong and in extreme bad taste." He also tweeted: "The organisers of that event in Windrush Sq last night do not speak for or represent the people of Brixton."

The former Labour prime minister Tony Blair criticised the "parties". He told the BBC: "I think that's pretty poor taste. You've got to, even if you disagree with someone very strongly, particularly at the moment of their passing, show some respect."

The Metropolitan police say those wishing to protest at the funeral should contact them so "their right to protest can be upheld". It is a tactic and language used by the Met in their operation to police the Olympics, which senior officers regard as being a success.

Police will also be looking with care at the threat posed by dissident republican terrorists. Patrick Mercer, the Conservative MP for Newark and security expert, who served in Northern Ireland as platoon commander while Thatcher was prime minister, told the Guardian: "Baroness Thatcher's funeral is bound to excite dissident Republican ambitions. It is something I know the security services are taking very seriously.

"I remember distinctly her visit to us after the Warrenpoint and Lord Louis Mountbatten killings [in August 1979] and, of course, she was identified as a major hate figure by republicans during the hunger strikes of 1981."

It is understood that security assessments have suggested dissident republicans would like to use the funeral to make a show of force. But the assessments have suggested that any threat is likely to be in Northern Ireland because they lack the resources to mount a major operation in Great Britain.

The guest list may provide something of a diplomatic headache for the government and the Thatcher family. Silvio Berlusconi's Freedom party said it had not yet been decided whether or not the former prime minister, who praised Thatcher lavishly in a statement on Monday, would be travelling to London.

Giorgio Napolitano, Italy's 87-year-old president and a former communist, "will definitely not" be attending the funeral, said a spokeswoman for the presidency. She said it was a question of protocol as Thatcher was not a head of state.

A spokesman for the office of Mario Monti, Italy's caretaker technocratic prime minister, said that a final decision had not yet been taken on whether he would attend, but that it was thought likely he would not.

The Egyptian presidency says it will send a representative from the embassy but has not yet decided who.

Thatcher's controversial standing in the world was highlighted when Bob Carr, the Australian foreign minister, described her as "unabashedly racist". In an interview with the Lateline programme on ABC TV, Carr related a conversation with Thatcher after her retirement in which she warned of the challenge to Australia of immigration from Asia.

Carr, whose wife is of Malaysian origin, said: "She said something that was unabashedly racist, where she warned Australia, talking to me with Elena [his wife] standing not far away against Asian immigration, saying that if we allowed too much of it we'd see the natives of the land, the European settlers, overtaken by migrants. I couldn't believe it."
http://www.guardian.co.uk/politics/2013/apr/09/margaret-thatcher-funeral-security