ePolitix.com profiles the key constituencies in the run-up to the 2005 general election.

On Sunday, Tony Blair chose this North London marginal for a major election rally.

The prime minister repeatedly warned against the danger of disillusioned Labour voters switching to the Lib Dems and allowing the Conservatives in "through the back door".

The choice of venue was carefully made, as this is just the type of seat where that might happen.

Labour's Joan Ryan is defending a 2,291-vote majority over the Tories in a seat which has been won by the party that went on to form the government in every election since it was created.

The northernmost constituency in London, this seat is mixed in character, with tower blocks to the east and an industrial area around the Cambridge Road.

On the other side of the M25 London's sprawl is arrested by more rural, green belt areas towards Hertfordshire.

The constituency is nowhere near as ethnically-mixed as most London seats, even those nearby. Over 90 per cent of the population here is white.

Nick de Bois is the Conservative challenger, a local businessman who also contested the seat in 2001.

Entrepreneurial spirit obviously flows in his blood: he reveals in his online campaign diary that his daughters have refused to canvass for him unless they are paid.

Controversy

He has already attracted controversy as one of five Tory candidates accused by the Independent on Sunday of running a hardline campaign on immigration.

De Bois quickly hit back, saying the newspaper's article "changed words, removed sentences and altered the meaning" of his literature, and lodged an objection with the Press Complaints Commission, recently securing a retraction from the newspaper.

But he also faced criticism over Tory leaflets on MRSA, with the chief executive of the local Chase Farm hospital saying the literature was "misleading".

Averil Dongworth said: "Our MRSA figures are not secret and have been given in detail to Mr de Bois.

"The gross exaggeration of these figures does not recognise the hard work carried out by our doctors and nurses throughout the year."

The slip was later blamed on a mis-type, and De Bois has moved his campaign on, saying pensions are a major issue on the doorstep.

"Labour have refused to rule out means testing for some pensioners, putting in doubt the whole state pension system," he said.

"Tony Blair just doesn't understand how humiliating means testing is for pensioners.

"They have worked hard all their lives, some have fought for this country, other have lost loved ones. But Labour will force you to come cap in hand to ask for what is rightfully yours.

"How older people are treated is a measure of a country, and Blair lets this great country down."

Chris Evans

Meanwhile, Labour's campaign in the seat is focusing on the party's priorities of education, health, low unemployment and the local environment.

Candidate Joan Ryan - a former teacher and deputy leader of Barnet Council - has also been a government whip, and is an ally of David Blunkett and a staunch supporter of ID cards.

She has also attracted the support of a famous Londoner. DJ Chris Evans was at the party at the rally on Sunday, to throw his weight behind the campaign.

Evans, who is the ex-husband of Doctor Who actress Billie Piper, branded the Conservatives the "Doctor Who" party.

He said: "[Howard] has somehow travelled in time. He is back, and his party are back, but they are back in time. If he is voted in on Thursday, the country will go back in time."

"I have met Tony Blair; I know deep inside me, I know he is a good man, I know he is an honest man," he added.

On May 5, Ryan will be hoping endorsements such as Evans' will make the crucial difference in protecting her slim majority.