The retired soccer star - who is expected to be making an appearance in the director's next movie - and the 'Snatch' filmmaker have surprised gym goers in London by taking part in group fitness classes, where they have teamed up to push one another to train harder.
A source told the Daily Mirror newspaper: ''Anyone can go to the gym they've been attending, so it was a real shock to see two huge names in there - especially in sessions for toning bums and legs!
''But they've also been working on their chests and abs, so it's clear they want to keep their full bodies in shape.
''David's obviously really fit, but it seemed like they'd teamed up in a bid to kick start the new year in a healthy way, as they went again the next day.
''And the pair have had quite gruelling workouts.''
The 38-year-old sportsman - who has children Brooklyn, 14, Romeo, 11, Cruz, eight, and Harper, two, with wife Victoria - recently spoke of his love of tough Soul Cycle classes.
He said: ''It's like spinning with a difference. There's music and choreography. There's 40 people in a room for 45 minutes, it's really hard and you come out there like you've just come out the shower.''
The BBC drama starring Aidan Turner returns to BBC One on September 4th.
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