The five on Tuesday crossed the North Atlantic from the Cuban bay aboard a Royal Air Force C-17 transport plane, accompanied by officers of the Metropolitan Police anti-terrorist squad as well as two independent observers.
Their flight touched down at 7:00 pm (1900 GMT) at RAF Northolt air base, northwest of London, from where they were being taken to a high security police station in west London for questioning.
The five British nationals left behind four compatriots in Guantanamo to face possible trial by a US military court.
Ruhal Ahmed, Asif Iqbal, Shafiq Rasul, Tarek Dergoul and Jamal al-Harith were repatriated to the United Kingdom.
Still in Guantanamo Bay are Feroz Abbasi, Moazzam Begg, Martin Mubanga and Richard Belmar, who according to Home Secretary David Blunkett had been captured in the "combat zone" in Afghanistan.
Two independent observers, one from the Muslim community, were on the flight which is also being video taped by police, London's Metropolitan Police said in a statement that anticipated concern about the five men's treatment.
Britain announced on 19 February that, after months of negotiations with Washington, the five - including three from the small town of Tipton, near Birmingham in the English Midlands - would be repatriated.
"The decision to transfer these detainees was made after extensive discussions between our two governments"
Department of Defence, USA
But it left open the option of arresting them immediately upon their arrival, probably under the Terrorism Act 2000 which would enable police to grill them for up to 14 days without charging them.
"The decision to transfer these detainees was made after extensive discussions between our two governments," the US Department of Defence said in a statement in Washington.
"The British government has agreed to accept the transfer of these detainees and to take responsibility to ensure that the detainees do not pose a security threat to the United States or our allies," it said.
The release of the five coincided with a trip to Washington by a British delegation of intellectuals and human rights activists to condemn what they see as a lack of basic due process for all Guantanamo detainees.
Around 660 prisoners suspected of being Taliban or al-Qaida fighters are being held without charges indefinitely as "enemy combatants" at Guantanamo Bay, a US naval base at the eastern end of Cuba.
Eighty-eight other prisoners of various nationalities have been released from Guantanamo Bay, and a dozen others transferred to their home countries for continued detention, including seven Russians turned over on 1 March.