by William Gallagher BBC News Online

Nervous of upsetting America, the new US version of Coupling proves hesitant and just not very funny.

The US version shies away from the smut of the UK one

You have to watch the US and UK first episodes of Coupling back to back to get the full shock: the British one is vastly better.

It is as if ER were the one made here and Casualty was American, the difference is that striking and is true from the writing and acting to how it is shot.

In the UK the opening episode had a mix of location filming with handheld cameras and good studio sets; in America it's like watching any of the three-wall, four-camera sitcoms videotaped in their dozens every year.

Consequently, NBC's very heavily promoted comedy, repeatedly touted as a potential successor to Friends, even looks cheap next to the BBC's version.

The UK version of Coupling has become a cult hit

But with Steven Moffat's original script surviving translation surprisingly intact, the problem may be made worse by the acting.

Throwaway jokes

Christopher Moynihan, for instance, is not allowed to have lines that are quite as embarrassing as Richard Coyle's in the British original but Coyle convinces you he means them.

None of the new cast punch their lines home: there are times when you do not realise something was a joke until you see it in the British one and laugh.

NBC is promoting Coupling as sexy and risqu� but it has backed down over throwaway jokes about swallowing and refused outright to allow Moynihan's Jeff to refer to girlfriends you can't get rid of as "unflushables".

None of which should really matter because Steven Moffat does not rely on shocks: the strength of his jokes is that they come backed up with an uncomfortable sense of truth.