UK Prime Minister Tony Blair has praised "positive" talks with Libyan leader Muammar Gaddafi, on the start of his week-long tour of Africa.
Mr Blair, who discussed defence, counter-terrorism and business with the Libyan leader, said relations had been "completely transformed".
He spoke as British oil giant BP announced a return to Libya after 30 years, in a gas exploration deal.
Mr Blair will also visit Sierra Leone and South Africa during the tour.
The Africa trip is his last major tour before stepping down as PM.
Speaking after a two-hour meeting in a tent outside the coastal city of Sirte, Mr Blair said BP's decision to return to operations in Libya marked a "huge investment".
He added: "I'd just like to say how positive and constructive the meeting with leader Gaddafi has been.
"The relationship between Britain and Libya has been completely transformed in these last few years. We now have very strong co-operation on counter-terrorism and defence."
He said the commercial relationship between the two countries was going "from strength to strength" and showed how relations could change.
"A few years back Britain and Libya could never have had this relationship," he added.
Britain and the US persuaded Mr Gaddafi to give up ambitions on nuclear weapons in 2003.
Later Mr Blair met relatives of the 400 Libyan children who were allegedly deliberately infected with the HIV virus by five Bulgarian nurses and a Palestinian doctor in 1998.
The medical personnel, who say they were made scapegoats for poor hospital hygiene, face the death sentence.
Mr Blair said relatives had suffered a great tragedy and told them there was much sympathy for them in the UK.
During his tour, he hopes to focus attention on Africa and climate change ahead of the forthcoming G8 summit.
He will travel to Sierra Leone, where he sent British troops to restore order in the early days of his premiership, and then on to South Africa.
The South African government has said Mr Blair will hold talks with President Thabo Mbeki and deliver a major policy speech on Africa during his stay in the country.
Mr Blair's official spokesman said the trip was about "showing that we need to keep re-engaging on Africa as a whole".
He said Sierra Leone was approaching its first elections since the UN left, and "that's only possible because of continuing engagement from countries such as ourselves".
The humanitarian crisis in the Sudanese province of Darfur is also likely to be high on the agenda as Mr Blair talks with African leaders.
Downing Street said that "all three countries he will visit illustrate, in different ways, the benefits of this government's active, values-driven foreign policy engagement with Africa".