Martin Sheen will bow out as President Josiah Bartlet after serving two terms.

Most recently, viewers have seen actors Alan Alda and Jimmy Smits battling to be elected as his successor.

The show won Emmy Awards for best TV drama in four successive years and has the record for most Emmys in a single season, with nine in its first year.

Set in the West Wing of the White House, the programme follows the administration of the fictional Democratic president.

Broadcaster NBC decided in January to drop the drama because ratings had declined.

Falling ratings

At its peak, it was among the most popular shows on US television with audiences of 17 million and frequent praised from critics.

However, the current season made its debut with 7.6 million viewers in a new Sunday night timeslot.

The West Wing's use of intricate terminology, delivered during punchy back-and-forth dialogues between the characters - could also baffle viewers unfamiliar with the finer points of US politics and law.

Actor John Spencer, who played chief of staff Leo McGarry, died last December after a heart attack.

In a sad coincidence, his character had also suffered coronary failure - but in the programme, McGarry recovered and returned to politics.

This final series of The West Wing had to be rewritten in order to fill the gap left by the death of the popular actor.

Old roles reprised

Former cast members agreed to return to the show as it approached its final episodes.

Rob Lowe reprised his role as Sam Seaborn, who had been the deputy communications director.

Lowe had left in 2003, with a dispute about his salary rumoured to be to blame.

Mary-Louise Parker and Emily Proctor - who is now one of the stars of CSI: Miami - have also come back to The West Wing.

The programme's creator, Aaron Sorkin, gained notoriety in 2001 when he was ordered into rehab after pleading guilty to drug charges.

Security staff at Los Angeles airport had discovered marijuana, rock cocaine and hallucinogenic mushrooms in his bag.

Sorkin left the show after its fourth series in 2003, with NBC bringing in a new team of writers.

Sunday's last-ever edition sees the inauguration of a new leader to replace President Bartlet.

Viewers in the UK must wait approximately three months to see it as digital channel More4 has only just shown episode 10 of the 22 in series seven.