Actor David Schwimmer has said he had the "time of my life" making his cinematic directorial debut with British comedy Run, Fatboy, Run - despite taking three years to complete it.
Schwimmer shot in Hackney and rejected "picture postcard" London
The 40-year-old, best known for his role as Ross in Friends, moved into film after directing 12 episodes of the hit US comedy.
But he has been attempting to make Run, Fatboy, Run, which is set in London and stars British comic actors Simon Pegg and Dylan Moran, since the final series of Friends ended in 2004.
"The biggest difference is that on a sitcom, you're on a soundstage so you have this controlled environment.
"You never have to worry about two of the biggest variables when you're on location - which are sound and weather," he told BBC World Service's The Ticket programme.
"We had over 50 locations around London on this film, and England is not known for its predictable weather - which was quite a challenge, especially when we're making a film on a tight budget.
"A tight budget makes every day count. If you don't get the shot, or get the scene done on that day, you're pretty screwed."
Run, Fatboy, Run had its premiere in the UK on Monday, almost exactly three years to the day since Schwimmer first confirmed it would be his first film as director.
At the time, the script, by Michael Ian Black, was set in New York - although its basic plot, about a man who enters a marathon to win back a girl he left at the altar on their wedding day, has not changed.
"As soon as I put it down, I called and said, 'I have to direct this'," Schwimmer said.
However, he initially found the process of getting the film going "very frustrating", in part because studio executives insisted he found a big name for the title role.
Among those Schwimmer suggested were Philip Seymour Hoffman, Paul Giamatti and Jack Black - but none was considered high-profile enough at the time.
Eventually the script was optioned by Material Entertainment, a company which aims to make films in London.
Schwimmer said he was about to quit - but then decided to involve Pegg, with whom he had starred in black comedy Big Nothing.
Pegg, who would eventually end up playing the eponymous "fat boy", rewrote and "Anglicised" the script, although Schwimmer insisted it had not required major work to be tailored to a British audience.
"We both find American and British humour equally funny, and not that different," Schwimmer said.
"If they're really strong, identifiable characters and really funny situations, then the comedy should be universal."
However, once the script was finished and filming under way, Schwimmer then found that the rights to the London Marathon - to feature in his big climax - had been acquired by another director.
So, he had to invent an alternative race, the Nike River Run. Sportswear company Nike were mentioned in order to save cash - they agreed to supply clothing for the fake race.
Simon Pegg tweaked the script for the British audience
Schwimmer now found he had to create a marathon using just 200 extras pretending to be 10,000 runners. Mostly, he explained, this was done by simply asking them to change costume once they were out of shot and run around again.
But despite the problems, he said he had "really loved" directing a film, and wanted to do so again - although it did not mean he would be giving up acting.
"I don't want to have to choose," he said. "I love acting just as much. It's also a hell of a lot of a shorter time commitment."