Thatcher died Monday.
Plans include a "ring of steel" between the Palace of Westminster and St. Paul's Cathedral to guard against attempts to interfere with the funeral procession, The Daily Telegraph reported. Members of Britain's armed forces will be standing guard as well along the two-mile route.
Scotland Yard also plans to deploy mobile units around the city.
Thatcher, who reshaped the country and the Conservative Party, is proving to be as polarizing in death as in life. While mourners will include world leaders, anarchists are planning street parties.
Some from Thatcher's political generation are unable to attend for health reasons, including Mikhail Gorbachev, the Russian leader who presided over the dissolution of the Soviet Union, and Nancy Reagan, whose husband was Thatcher's closest foreign ally, The Independent reported. Former South African President F.W. DeKlerk, who helped end apartheid there, will be present as a guest of Thatcher's family.
One world leader who is definitely not on the guest list is Argentine President Cristina Fernandez de Kirchner. Thatcher led Britain during the 1982 Falklands War with Argentina, and Fernandez, more recently, has called for negotiations over the Falklands Islands.