"Spectre" star Ben Whishaw, who leads "London Spy", said the TV series is the most demanding thing he has ever done.
Whishaw, 35, plays Danny, a troubled romantic who falls for a man named Alex (Edward Holcroft).
"London Spy", from thriller writer Tom Rob Smith, has also recruited an all-star supporting cast, including Mark Gatiss, Charlotte Rampling, Adrian Lester and Jim Broadbent, who plays Danny's confidant Scottie
The entire series, though, is told entirely from Danny's perspective, with Whishaw describing the experience of shooting "London Spy" as "very full-on", reported Digital Spy.
"The character's in every single scene. I don't think I've ever done anything quite as intense and demanding as this has been," Whishaw said.
