A British-Australian sailor murdered his new wife at sea and deliberately sank their catamaran in order to inherit her estate and end their "marital strife", prosecutors have alleged.

Lewis Bennett, of Poole, Dorset, was smuggling rare stolen coins when he was rescued alone off the coast of Cuba without Isabella Hellmann, the mother of his child, last May.

Prosecutors in the US have now detailed what they believe to be Bennett's motives, after the FBI charged him with murder.

Court papers filed this week also revealed Ms Hellmann's family bugged her apartment in Delray Beach, Florida, to listen to Bennett's conversations because they suspected him in her disappearance.

The newlyweds were sailing towards Florida in May last year when Bennett made an SOS call saying Hellman, a 41-year-old former estate agent, was missing and the vessel was sinking.