BBC News Channel

Bob Stewart MP, reflecting on his experiences as a soldier during the Troubles, said Martin McGuinness was "one of the people we were watching all the time".

He told BBC News "we would have had a solution in Northern Ireland a long time ago" if Mr McGuinness and his IRA allies had not "taken to the gun".

He added: "I'm really sad that he has died, but frankly I find it very difficult to forgive what happened in those early days."

The World at One
BBC Radio 4

Mark Eakin, who witnessed the 1972 Claudy bombing which killed his eight-year-old sister, said he "changed his mind" about Martin McGuinness.

He told Martha Kearney that years ago he would have "despised" Mr McGuinness, but said "I'm a great believer that if somebody changes their ways, to give them a chance."

Sinn Féin leader Gerry Adams paid a warm tribute to his friend Martin McGuinness, saying he had shown "determination, dignity and humility" throughout his life and during his recent illness.

The outgoing Ulster Unionist Party leader, Mike Nesbitt, said "no-one needed to die to get Northern Ireland to where it is today" but added that he found Martin McGuinness to be "straight-dealing" .

The Labour leader, Jeremy Corbyn, said Martin McGuinness played an "immeasurable role in bringing about peace in Ireland, after years as a key protagonist in the tragedy of the conflict".

"Martin played an absolutely crucial role in bringing about the Good Friday Agreement and a peace process which, despite difficulties, remains an example throughout the world of what can be achieved when the will is there," he said.

BBC News Channel

Jon Tonge, a British and Irish politics professor from the University of Liverpool, believes Mr McGuinness had possibly been on one of the most extraordinary political journeys ever seen.

Mr McGuinness started steering Sinn Fein in a political direction from the mid-1980s onwards - at considerable personal risk, he tells the BBC.

His move was not because the IRA was on its knees - indeed it was still capable of delivering huge bombs, such as those in 1996 in Canary Wharf and Manchester, he says.

What has surprised him, he adds, is the "generous and measured" responses from the likes of Theresa May and Tony Blair.

Bernard Purcell, editor of Irish World, says of Mr McGuinness: "His legacy is a power-sharing executive and the fact that his political movement has embraced constitutional politics."  

SDLP leader Colum Eastwood has joined other politicians in recognising the journey Martin McGuinness made from paramilitarism to politics.

The World at One
BBC Radio 4

Mark Eakin, who witnessed the 1972 Claudy bombing which killed his eight-year-old sister, said he "changed his mind" about Martin McGuinness.

"Many years ago I would have despised him," he told BBC Radio 4's World at One .

He said the atrocity, where nine people died, was "like the Blitz", when three car bombs exploded in the Londonderry village.

But during a later phone conversation, he said Mr McGuinness agreed the attack was "indefensible".

"He did apologise and said Claudy should never have happened," Mr Eakin said.

"I’m a great believer that if somebody changes their ways to give them a chance."

A book of condolence for Martin McGuinness has been opened at the Guildhall in Londonderry. 

Image source, Pacemaker

Jonathan Powell was Tony Blair's chief negotiator in talks that led up the Good Friday Agreement in 1998 - he tells BBC's World Update that Martin McGuinness was likeable despite his violent history. Listen below. 

The First Minister of Wales, Carwyn Jones, says Martin McGuinness was "vital in bringing peace to Northern Ireland".  

Image source, AFP/Getty Images

"When he spoke, people listened," he says. 

"That presence explains much about how he was able to build bridges across the political divide. My thoughts are with his family and friends today."

"We had a shared interest in cricket which was something I hadn't anticipated," Northern Ireland Secretary James Brokenshire said about his relationship with the former deputy first minister Martin McGuinness.

Former SDLP leader John Hume and his wife Pat have paid tribute to Martin McGuinness, saying he left an "indelible print on politics in Ireland".

"Our starting points on the approach to finding a solution to the divisions on this island were very different but there can be no doubt Martin was deeply committed to the agreed Ireland of the Good Friday Agreement and its power-sharing institutions," they said. 

"He played a very important role in our peace process and his courageous, generous and gracious gestures as deputy first minister were offered in a spirit of reconciliation and peace building." 

The Taoiseach (Irish Prime Minister) has joined in tributes to former deputy first minister Martin McGuinness following his death in the early hours of this morning.

The World at One
BBC Radio 4

Jonathan Powell was Tony Blair's chief of staff and worked closely with Sinn Fein in the years running up to the Good Friday Agreement and beyond. 

On Radio 4's World at One, Mr Powell describes the first time he met Martin McGuinness in October 1997, where he "refused to shake his hand", a gesture, he says,  he later regretted. 

Mr Powell told Martha Kearney his feelings towards the IRA were coloured by the fact that they had "shot his father through the ear in an IRA ambush". 

Sinn Féin's northern leader, Michelle O'Neill, has paid tribute to Martin McGuinness, whom she succeeded when he stepped down in January.