By Mark Simpson BBC Ireland correspondent

Never underestimate the determination of a quiet man, even when he is the new secretary of state for Northern Ireland.

Paul Murphy is a softly-spoken Welshman, with few, if any, enemies in politics.

During his time in Northern Ireland from 1997-99, when he served as political development minister, no-one can remember him raising his voice.

This is no mean feat, given that he dealt with politicians like the DUP leader, Ian Paisley, and the Sinn Fein president, Gerry Adams.

John Reid seems to have been surprised by move

One former colleague remembers Mr Murphy as a skilled problem-solver during his time in Belfast.

"He relied on logic, rather than emotion. He thought before he said things, rather than rushing in," said the former colleague.

"In many ways it's a clever move by the prime minister to send him back to Northern Ireland, he'll be a good honest broker.

"Mind you, some of his friends might say 'poor Murph'. He's being taken out of the place he knows and loves (Wales) and sent back to deal with all the problems in the peace process."

Predecessors

He will not have to do it on his own. The pattern in recent years has been that no matter how good the secretary of state is, Tony Blair retains a hands-on role.

That happened in Mo Mowlam's time, and it also happened when Peter Mandelson was Northern Ireland secretary.

Unlike the last secretary of state, Dr John Reid, who came to Belfast two years ago with no experience of the peace process, Mr Murphy knows the situation well.

Prime Minister Tony Blair has maintained hands-on role

He was at the heart of the negotiations which led to the signing of the Good Friday Agreement in 1998 and therefore knows all the local politicians by name.

His job now is straightforward - to ensure that the Good Friday Agreement survives.

To do that, he needs to somehow restore the power-sharing executive at Stormont which Dr Reid was forced to suspend last week. That could take months, if not years.

Tough challenges

Mr Murphy's first task is therefore to try to kick-start some movement within the republican movement. He will know that devolution cannot be resurrected without a significant shift from the IRA.

Before that can happen, the IRA will be waiting to see what the government is going to do about further police reform, and the possible reduction of security installations and troop numbers.

At the same time, the battered relations between the political parties in Belfast need to be repaired in order to stop a bad situation becoming any worse.

For Mr Murphy, there will be little time to relax in the coming weeks and listen to the classical music which he loves.

One of the consolations he has is the fact that the Northern Ireland secretary has two castles - one at Hillsborough and one at Stormont.

Reid seemed surprised

Apparently, Dr Reid joked at a private meeting recently about being the "two castles cabinet minister" as opposed to being the "two jags minister".

Dr Reid's departure is a huge shock - not least to himself.

On Tuesday morning, at a breakfast meeting with journalists, he was firmly focused on the job in hand and in spite of the problems facing the peace process, he seemed to relish the challenge ahead.

There was no talk of going back to London. It didn't even seem to be on the radar.

Within 48 hours he was packing his bags, and preparing to hand over control of Northern Ireland to someone else.

The Reid regime is over. It's now Murphy's law.