Samantha Davis, 53, died at University College Hospital in London on March 24 last year
Officers were alerted to a body in the River Thames in Maritime Quay in east London on Sunday at 9.03am, the Metropolitan Police said.
The dub poet, who appeared in hit BBC show Peaky Blinders, died at the age of 65 in December 2023, shortly after being diagnosed with a brain tumour.
The Metropolitan Police said a man, 38, was arrested on suspicion of assisting a foreign intelligence service after he arrived in the UK on March 19.
The officers were responding to reports of a person carrying a firearm at Milton Keynes railway station this afternoon