BBC's Mark Devenport: "It came as a bit of a surprise"

The Orangemen spent about an hour in Downing Street on Monday in a bid to end the four-month stand off.

A spokesman for the prime minister said the meeting had been "positive and constructive".

He added: "The prime minister listened carefully to the points raised by the Order and promised to keep in touch."

A small group of loyalists have maintained a protest in Drumcree since July to demand the right to march in the area.

Orangemen continue to demand the right to march down the Garvaghy Road

The continuous demonstration at the hill-top Drumcree Parish Church began after an annual parade was stopped from going into a mainly Catholic neighbourhood.

The enforcement of the ruling by the Parades Commission led to violent clashes between thousands of protesters and police.

The worst moment came when demonstrators started to attack nearby properties, throwing fire bombs in to houses in the area.

This led to three brothers - Richard Quinn, 11, Mark, nine, and Jason, eight - dying in a sectarian arson attack on their home.

The numbers of Orangemen in Portadown has reduced considerably in the months since, but a small presence has continued.

A token demonstration has continued at the Portadown church since July

Hundreds protested in the town again in October to demand their right to march, despite objections from the Quinn family.

The Church of Ireland Archbishop of Armagh, Dr Robin Eames, has called on all sides to try to reach a solution on Drumcree.

The Orange Order met last week with Archbishop Eames and his Catholic counterpart Archbishop Sean Brady, but neither church leader has commented on the discussions.

Those staging the round-the-clock protest in Drumcree have vowed to stay until they are granted permission to march down the nationalist Garvaghy Road.

But the latest development is described highly significant by those following the dispute.

Row over Ahern comments

The UK prime minister will become the first British politician to address a joint session of the two houses of the Irish parliament on Thursday.

Mr Blair also plans to meet both Northern Ireland's first minister and his Irish counterpart this week to seek to move forward the province's peace process.

Bertie Ahern: Expects a united Ireland

Both David Trimble and Bertie Ahern will hold talks with Mr Blair on stumbling blocks to full implementation the Good Friday Agreement.

The meetings come after a fresh row broke out after Mr Ahern said he could envisage a united Ireland within 15 years.

He said: "I make no secret of the fact that I would hope in the fullness of time that people will see that it is working together on this island that will make more sense than looking to Westminster, and that they will take a decision to move away from that.

It might not happen within his lifetime, he said, but would certainly come.

"I don't know how long I will live, but I do think it will happen. It might take 15 to 20 years."

His remarks angered unionists, including Ulster Unionist MP Jeffrey Donaldson would branded them "unhelpful and unrealistic".