Pakistan politician Altaf Hussain has reportedly been arrested at a home in northwest London on suspicion of money laundering.
The 60-year-old self-exiled founder of the liberal political party Muttahida Qaumi Movement runs the party from London after he was granted political asylum in 1992.
He was arrested on Tuesday morning at his Edgware home, the Express Tribune reports, news of which wiped 780 points off the Karachi Stock Exchange.
Hussain is one of the country's longest serving politicians having grown up in a middle-class family.
Muttahida Qaumi Movement mainly represents Urdu-speaking descendants of Muslims -- known as Mohajirs -- who moved to Pakistan from India in 1947.
It rocketed in the polls and became the third largest political party in Pakistan's National Assembly.
Hussain requested political asylum in the UK in 1992, later gaining British citizenship, after he and his family came under attack.
The Met Police said in a statement: "Officers have this morning (3 June) arrested a 60-year-old man on suspicion of money laundering. The arrest took place at a residential address in northwest London.
"Officers are at present searching the address. Not prepared to discuss further at this stage."