Although it's been running since 2003 and is one of America's highest-rated comedies, I only recently discovered the joys of Two and a Half Men. In it, Charlie Sheen plays Charlie Harper, a hard-drinking womaniser who refuses to modify his hedonistic lifestyle when his newly separated younger brother, Alan, moves with his 10-year-old son into Charlie's Malibu beachfront home. Sheen is a revelation in the part, revealing an unexpected gift for comedy and clearly enjoying hamming up his bad-boy reputation. And Two and a Half Men is a good example of how respectable it's become for movie actors to revive and complement their careers by appearing on the small screen.

Once upon a time, it would have been considered career suicide for a film actor of any note to deign to appear on television -- unless it was an in-joke walk-on, or a chat-show interview. From its earliest days in the 50s, TV was where you started your acting career, and sometimes where you finished it, but it was no place for a film star to be caught plying his trade.

In the 70s, it was okay for ageing stars such as Raymond Burr and Howard Keel to be put out to graze on shows such as Ironside and Dallas, but only once they had accepted that this would effectively mean the end of their film careers. Even a big star such as James Garner had to accept that his movie days were pretty much over once he committed to The Rockford Files. Television was most definitely looked down upon by the studios, and was seen as a forbidden land of poor scripts and bad acting.

Not any more, of course. Since the late 90s, it's Hollywood that's struggled to keep up with the excellence of TV writing in both comedy and drama in what's now considered a small-screen golden age. And, as a consequence, even A-list film actors have been keen to get in on the act.

The current trend for movie stars fronting up TV dramas probably began with The West Wing, and Charlie Sheen's father. Martin Sheen must have thought long and hard about whether or not to accept the role of President Jed Bartlet in Aaron Sorkin's ambitious political drama: though not at the very top of his career in 1999, he was still considered one of Hollywood's most respected character actors, and a bad TV show might have put paid to all that.

Instead, of course, The West Wing became one of TV's most celebrated dramas, and its reassuringly moral White House grew ever more popular as the ineptitudes of the Bush administration became clear. And Sheen's success as Jed Bartlet persuaded other film actors to dip their toe in TV waters. Rob Lowe and Stockard Channing had been with Sheen on The West Wing from the start, but Alan Alda (who'd started his career on the small screen) later returned to join them. By the early 2000s, the show was becoming part of a broader trend.

A big star in the 80s, William Petersen was struggling a bit as a film actor by the late 90s, but his decision to accept the lead role in a new CBS TV crime drama in the year 2000 would eventually make him one of the highest-paid actors in America. With its slick editing and sharp storylines, CSI: Crime Scene Investigation brought Hollywood production values to prime-time television, but it needed a charismatic star to anchor its appeal, and Petersen had it in spades.

He was excellent as the eccentric CSI night supervisor Gil Grissom, and when he eventually decided to hang up his lab coat late last year in the middle of the ninth season, the producers made sure they had a well-known film actor -- Laurence Fishburne -- to replace him. In fact, even the show's spin-offs managed to attract movie actors: Gary Sinise currently heads the cast of CSI: New York, while David Caruso is the star of CSI: Miami.

On the comedy front, Sarah Jessica Parker had taken a considerable risk by attaching herself to the HBO comedy Sex and the City, which first aired in late 1998. It was something of a punt, because she risked jeopardising a very promising film career that had seen her star in films such as Steve Martin's L.A. Story and Tim Burton's Ed Wood.

Maybe she had an inkling of how hugely successful the irreverent New York comedy would be, but was clever enough to become a producer relatively early on, thus maximising her already considerable income.

Kiefer Sutherland was more of a mid-table film actor than his celebrated dad, but was still performing respectably in Hollywood when he agreed to front 24. The brilliantly paced action series made most of the thrillers Hollywood was pumping out look pretty tame. Now in its seventh series, it has made Sutherland one of the biggest stars on television, and he's again being offered significant film roles. Dad Donald would later follow in his footsteps by taking on a key role in the edgy soap opera Dirty Sexy Money.

The medical drama ER, which finally finished its marathon 15-year run earlier this year, is most famous for having kick-started the film career of one George Clooney. However, so revered did the multi-Emmy award-winning drama become that it started to attract appearances from some very established film stars. Sally Field began the trend in 2001, and was followed by the likes of Don Cheadle, James Woods and, most significantly, Forest Whitaker, who'd just completed his Oscar-winning turn in The Last King of Scotland in 2006 when he appeared in a series of ER episodes as a stroke victim. This was a real sign that the stigma of film stars appearing in TV dramas was finally at an end.

Once The Sopranos was up and running, film folk such as Steve Buscemi began muscling in on the act. Apart from playing Tony Soprano's ill-fated cousin, Tony Blundetto, he also directed one of the show's best-ever episodes, Pine Barrens. Seventies icon James Caan emerged from the woodwork to play the harried chief security officer at a busy casino in the NBC drama Las Vegas, while James Woods headed up the CBS legal drama Shark. And the surreal, cult comic drama Boston Legal was graced by the presence of James Spader, William Shatner and Candice Bergen.

Sometimes, when a show makes a critical impact in its first series, its ability to attract movie folk is significantly enhanced. Glenn Close and Ted Danson were the big stars of the first run of the innovative thriller series Damages, Rose Byrne being more of an up-and-comer. But for the second season, heavy-hitters such as William Hurt, Marcia Gay Harden and Timothy Olyphant had been added to the mix.

Closer to home, Gabriel Byrne has won considerable acclaim for his portrayal of the long-suffering shrink Paul Weston in the excellent HBO drama In Treatment. And any idea that this would somehow interfere with his film career now seems decidedly old-fashioned, as he has continued to mix his TV work with films. As, for that matter, have Alec Baldwin (30 Rock), Thandie Newton (ER), Felicity Huffman (Desperate Housewives), Anna Paquin (True Blood), Minnie Driver (The Riches), Ray Liotta (Smith) and Geena Davis (Commander-in-Chief).

Finally, TV drama has become thoroughly respectable.

- Paul Whitington