BBC Northern Ireland's chief security correspondent Brian Rowan has been studying their form.

Hugh Orde
He is policing's marathon man - a five times runner in the London event with a best time of 3 hours 32 minutes for the 26 miles 385 yards.

Hugh Orde: Finucane investigation

And for each mile of that marathon distance, Hugh Orde, has almost completed a year of policing service.

He joined the 'Met' 25 years ago when he was in his late teens and at 43, has now climbed to the rank of deputy assistant commissioner.

For the past two and a half years he has been travelling to Northern Ireland as head of the outside police team investigating the murder of the Belfast solicitor Pat Finucane and probing allegations of security force collusion.

The report of the Stevens team investigating the killing is due soon and one source has suggested it will be "Patten with attitude" - a reference to the controversial report on police reform.

Orde's investigation has given him a close-up look at the most controversial aspects of policing here.

He has been examining how the Special Branch functioned.

His findings, which will be written into the report of the Metropolitan Police Commissioner Sir John Stevens, will add to the debate on the future of the "force within a force" as Special Branch has come to be described.

Alan McQuillan
He joined the RUC in 1976 as the first graduate entrant under the accelerated promotion scheme.

Alan McQuillan: Belfast commander

He rose quickly through the ranks to become a superintendent in 1990.

He left the RUC in 1995 to become assistant chief constable in the Gwent Constabulary in Wales before returning three years later at the same rank.

McQuillan is currently the operational police commander in Belfast and is probably the best known of the three contenders.

The Holy Cross Girls' school protest and the street violence in north Belfast have regularly put him onto television screens over the past year.

Chris Albiston
Chris Albiston has recently taken charge of the PSNI's Special Branch and Criminal Investigation Department.

Chris Albiston: Served in Kosovo

He is a modern history graduate of Exeter College, Oxford, who joined the Metropolitan Police in 1975.

Albiston transferred to the RUC in 1989 and was appointed deputy sub-divisional commander in Lisburn.

He progressed through the ranks until he became an assistant chief constable in May 1998 when he took over responsibility for management support.

In January 2001, Albiston took on a high-profile role when he served as Police Commissioner with the United Nations Mission in Kosovo.

During his year there he was responsible for leading the 8,000-strong force of international and local officers who policed the troubled Balkan region. The RUC sent 60 officers.

Interviews are scheduled for 29 May and eight members of the board will decide who should succeed Sir Ronnie Flanagan.

The final appointment must be approved by John Reid

They are the chairman and the vice chair Professor Desmond Rea and Denis Bradley; three politicians Joe Byrne (SDLP), Fred Cobain (Ulster Unionist) and Sammy Wilson (DUP); and three independents, Pauline McCabe, Suneil Sharma and Barry Gilligan.

Their choice has to be endorsed by Northern Ireland Secretary John Reid.

The province's acting chief constable, Colin Cramphorn, has not applied.

He is looking for a job elsewhere and has recently been interviewed for six chief constable posts in England and Scotland without success.

Fermanagh woman Maria Wallis, who was being talked about as one of the favourites to succeed Sir Ronnie Flanagan, withdrew from the race in Northern Ireland after her recent appointment to the chief constable post in Devon and Cornwall.

'Charismatic'

But no-one is calling the result in this contest which is being characterised as a race to the line.

One Policing Board source told BBC News Online: "Whoever gets it has to be charismatic enough to lead the organisation through the change.

"He has to give some confidence to ordinary people that the increase in crime - burglaries, car crime, drugs - will be seriously addressed.

"People in the community are beginning to lose confidence in the police."

Another board source summed up the contest: "All three can have no illusions given their working knowledge of policing (in Northern Ireland) - no illusions about the range of change and the issues, past and future, that need to be tackled.

"It's a genuine three horse race and it could be a photo finish."

Who then will get their chest through the line first?

We will know soon. The board hopes to announce its "winner" next month.