I am not Spock: how some actors never manage to escape from their most famous characters

Timing, as Doctor Who would probably agree, is everything. After just one series as the intergalactic time traveller, Christopher Eccleston has bowed out of the role of Doctor Who for fear of being typecast.

Timing, as Doctor Who would probably agree, is everything. After just one series as the intergalactic time traveller, Christopher Eccleston has bowed out of the role of Doctor Who for fear of being typecast.

Eccleston, 41, who was previously best-known for starring in gritty dramas, is worried that the role which made household names of the actors who played the part before him will damage his future "artistic aspirations". And he might be right.

Even the most cursory glance through the film and television hall of fame provides ample evidence of how a single performance can cling, limpet-like, to an actor's CV.

Once an actor is stored as a certain character in the public's imagination, there is little or nothing a performer can do to erase the image.

"Typecasting happens and if you are in a position where you can avoid it, it is best to do so," said Niki Winterson, an agent at Michael Garret Associates, a London-based agency which represent actors working in theatre, musical theatre, television, film and commercials.

"There is more to the business than just making money. Most actors come into the profession because they want to play different roles. If they just wanted to make money they would go into banking instead," Ms Winterson, who specialises in finding film and television work for her clients, said.

She added: "Most performers have needs and desires which are linked to being as creative as they possibly can be. Once an actor is typecast they are by nature not going to be able to do everything they want to do to the full extent of their ability. I am sure that's partly what's in Christopher Eccleston's head."

However, while some actors strive to develop their talents with a variety of character roles, others spend their entire careers playing one type of person or developing a particular image which they use in almost every performance.

Hollywood greats such as Errol Flynn or John Wayne only played heroic, macho characters, whether it was as cowboys, battle-hardened soldiers or swashbuckling sea captains.

More recently Britain's Hugh Grant has found a niche playing mild-mannered, foppish British gentlemen, while Gary Oldman is often cast as a villain.

Although some actors realise they are being typecast and use it to their advantage, others kick against it but find that despite their best efforts the problem can never be overcome - and they sometimes live to regret trying.

In 1930 the Hollywood star Bela Lugosi turned down an offer to play the monster in Frankenstein. He had just had a massive cinematic hit as Count Dracula and he rejected the Frankenstein role because he didn't want to be typecast as a horror movie star. Boris Karloff took the monster role instead and Lugosi was forced to share the horror spotlight.

Unfortunately, Lugosi's decision was one the "serious" actor regretted for the rest of his life. Karloff became the bigger star, while Lugosi ended his career in 1956 with a performance in what is frequently voted the worst movie ever made, Plan 9 From Outer Space.

John Cunningham, an experienced, Rada-trained actor with hundreds of television and film credits to his name, said: "Nobody wants to be stuck in something which you think might damage future opportunities.But if a niche character or role comes along it would be madness not to consider it.

Mr Cunningham, who also teaches other professional performers through his London-based Actorclub workshops, said: "I don't think it is so much being typecast - in the way that Hugh Grant has been in specialising in a certain type of role - which bothers most actors, it is being remembered for only one part as that could affect what they are allowed to do in the future. I don't think Christopher Eccleston fears being typecast but rather that it would influence the way people think of him when he takes on other roles.

"The moment he wanted to play Macbeth or Noël Coward people would always think of him as Doctor Who if he did too many episodes."

ROLES THAT DEFINED ACTORS

Mr Spock

Name: Leonard Nimoy

Known for: Playing Spock in the original 'Star Trek' series between 1966 and 1969

Style: Emotionless logician of the Starship 'Enterprise'.

He has never been able to shake-off the pointy ears image despite other film and television roles. The show was one of the most successful in television history, spawning cartoons, six films, four spin-off television shows and countless novels

Margo Leadbetter

Name: Penelope Keith

Known for: Playingstuck-up snob Margo Leadbetter in 'The Good Life' for three years

Style: Posh totty

Keith went on to play similar middle-class women, most notably in 'To The Manor Born'

Rachel Green

Name: Jennifer Aniston

Known for: Playing Rachel Green in the comedy show 'Friends' for 10 years

Style: Sexy girl next door

Despite other roles, her squeaky clean image has haunted her career

Count Dracula

Name: Christopher Lee

Known for: Playing the vampire Count Dracula

Style: Sinister

Although he appeared as Dracula in just eight films, it is the role that he is probably best remembered for

Ken Barlow

Name: William Roach

Known for: Playing Ken Barlow on 'Coronation Street' since show began

Style: Dull but reliable.

Roach sued 'The Sun' when it confused him with his 'boring' character