Italian Cardinal Angelo Scola is going to be the next Catholic Pope, at least according to UK bookies that agree in identifying the 71-year-old archbishop of Milan as the front runner to replace Benedict XVI.

However, a few hours before the start of the conclave to elect a new pontiff, the race is tighter than what the odds suggest.

"We have had five or six different favourites since Benedict announced he was going to resign and I won't be surprised to see a new favourite coming up by tomorrow evening, if Cardinals haven't elected a new Pope yet," said Joe Crilly from bookmaker William Hill.

In the Vatican secrecy rules when it comes to elect a new Pope and history has yielded plenty of surprises.

From Tuesday, the 115 cardinal-electors taking part to the conclave are to be sheltered from the outside world, until a white smoke rises form the Holy See, announcing a new pontiff has been elected.

Secluded in the Vatican Hotel the clergymen are prohibited the use of phones and internet and even the reading of newspapers, making it impossible for indiscretions to leak out of the Holy See and help oddmakers in picking up their favourites.

"The odds are calculated by considering the strengths and experiences that are desirable for any potential Pope (or Papabile) to have. Each candidate is priced based on how many of these boxes that they tick, for example communication skills, languages, previous positions held," explained Scott Rory from Paddy Power. "We also take into account the money that is placed."

Scola is favourite at William Hill (9/4), Paddy Power (2/1) and Ladbrokes (2/1).

"Together with Peter Turkson, Scola has been the most continuous in attracting bets," Crilly said.

"However the Pope-market is incredible in its volatility. I can just compare it to bets on who will be the next Man United manager after Sir Alex Ferguson: odds change on daily basis."

Real Madrid Manager Jose Mourinho is currently listed as favourite to succeed Sir Alex on Man United's bench.

"Scola started to move up the betting as it became clear that an Italian Pope is a strong possibility," said Rory.

"Scola is suitably conservative. He has controlled high profile and significant policy areas for each of the previous two Popes. He is a former Patriarch of Venice and the current Archbishop of Milan - two dioceses that remarkably have produced five of the eight Popes who reigned during the 20th century."

Ghana's Turkson, 64, has been widely tipped as the top African contender for pope and the first possible black Pontiff in Catholic Church's history.

He is listed Second to Scola with 4/1 at Paddy Power and Ladbrokes and 7/2 at William Hill.

However Brazilian Cardinal Odilo Scherer, 63, has been coming up strong, climbing the odds' ranks in the last few.

"The day he stepped down, Benedict talked to Scherer for a long time and his odds have rocketed since, people believing he is the Pope's favourite," Crilly said.

Scherer is listed with 5/1 at William Hill, Paddy Power and Ladbrokes.

A diametrically opposite path to Scherer's has been experienced by Canada's Cardinal Marc Ouellet (12/1 at Paddy Power and Ladbrokes; 9/1 at William Hill), who heads the powerful Vatican's office for bishops.

"The Canadian was very well backed at the start and soon became the favourite, but he has dried on in the last couple of weeks."

As in any race worthy of its name, even the pontiff run has its dark horses.

"Those Cardinals that are quietly keeping a steady place in the betting are Peter Erdo of Hungary, Christoph Schonborn of Austria, Sean O'Malley of USA and Luis Tagle of Philippines," suggested Rory.