Lebanese Prime Minister Saad Hariri arrived in London to meet with British officials and members of Parliament.
Hariri's visit comes as political tensions in Beirut are strained by an investigation into the assassination of the prime minister's father, Rafik, in 2005.
The Special Tribunal for Lebanon is expected to release its findings by the end of the year, upsetting a delicate political balance in Beirut that has Hezbollah as a member of the government.
Hezbollah, which is believed to have played a role in the plot, said the investigation is part of a broad Israeli conspiracy.
Hezbollah reacted with outrage last week after STL investigators carried out interviews at a women's clinic in Beirut. British Foreign Secretary William Hague, however, said Lebanese independence depended in part on the autonomy of the special tribunal.
"That is an important process and we have supported Prime Minister Hariri in resisting attempts to derail that process," he said in a statement.
Hariri said he welcomed London's extension of friendship and "support for Lebanon, its sovereignty and its independence."