Murder in Hyde Park

An early-morning jogger is murdered in Hyde Park. It's the centre of London, but no one saw him enter the park, no one saw him die.
He carries no identification, only a water-logged phone. As the pieces unravel, it's clear that the dead man had a history of deception.
Is the murderer one of those that loved him? Or was it someone with a vengeance?
It's proving difficult for DCI Isaac Cook and his team at Challis Street Homicide to find the guilty person - not that they'll cease to search for the truth, not even after one suspect confesses.