Allawi was close to Saddam Hussein in the early 1970s and he was sent to Britain for a higher degree in neurology.
He became the coordinator of the Baath party in the UK and also worked for Iraqi intelligence.
Shortly afterwards, Allawi is believed to have started planning a coup. When Iraqi intelligence found him out, he was summoned to Baghdad. Allawi refused to go and became a defector.
In 1978, he claimed that an assassination attempt on his life had taken place in London. He alleged the attack was ordered by Saddam Hussein.
Allawi formed the Iraqi National Accord (INA) in 1991 with the backing of the CIA and Britain's MI6. The organisation attracted disillusioned former Baathists who wanted to orchestrate a coup from within the Iraqi army.
But the INA will most likely be remembered in Britain for passing on to MI6 a report from an Iraqi officer who made the now-infamous claim that Iraq could launch weapons of mass destruction within 45 minutes.