Lost in Translation was the first film shown on the rebranded Film4

The film channel became free at the weekend, securing 735,000 viewers for a screening of Lost In Translation.

It was the most-watched digital TV station in multi-channel homes, according to Channel 4.

Mr Sykes, who has been with Film4 since it began in 1998, will leave in September. "This is the logical moment for me to move on," he said.

Audience aim

Channel 4's director of television, Kevin Lygo, praised Mr Sykes for his "painstaking hard work" and "unrivalled knowledge and experience".

"We know he will be successful in whatever he decides to do in the future," he added.

Film4's relaunch saw it become available on Freeview for the first time, having previously only been available to 300,000 cable and satellite subscribers.

Channel 4 hopes that making the channel free, and putting advertisements into films for the first time, will increase audiences and revenue.

Mr Sykes, who was also the manager of entertainment channel E4 from 2000-2001, has not announced his future plans.