HE began studying to be a chemical engineer but ended up changing university and career and dedicating his life to the Church.

Now Reverend John Chalmers will become the new Moderator of the General Assembly of the Church of Scotland when it gathers in Edinburgh in May.

The Kirk's appointment committee met in "extraordinary circumstances" to decide who would take over from the Rt Rev Lorna Hood after Rev Dr Angus Morrison had to stand down due to ill health.

The 61-year-old moderator designate, an expert in Church law, will steer debate on the issue of gay ordination as one of his first tasks in the year-long role that includes ambassadorial duties.

He has spent his life helping others and has recently aided his youngest son John-James through recovery after he was wounded in Afghanistan while serving in the Royal Marines. The 25-year-old suffered arm, leg and facial injuries in blast, which killed two of his comrades.

Mr Chalmers is said to be well placed to take on the role of moderator at short notice as he is the long-standing Principal Clerk to the General Assembly, which involves providing the annual gathering with legal advice.

Mr Chalmers said it was an "unexpected privilege and a real honour to be entrusted with this role at this time".

Addressing the "urgent challenges" that face the Church, he said: "My focus will be on those things that unite us.

"Within the Church we have to learn to live with our differences. We have an urgent need to recruit women and men to train to be ministers and it's time to let society know that there is something very meaningful about living the life of faith."

He said the Church had to be an "instrument of healing and reconciliation in post-referendum Scotland" and promised to "champion the right of the most disadvantaged both at home and abroad".

"I will want to tell the story of a Church which cares about the values by which Scotland lives, which cares about the conditions in which people live and which puts its money where its faith is, in the work it does amongst the most vulnerable and marginalised."

Mr Chalmers has spoken about the horrors of war after his son was injured in Afghanistan in 2011. John-James was treated at Camp Bastion, then flown to Selly Oak in Birmingham.

Last year, Mr Chalmers told of how his son was still recovering. He said: "Until now I never realised the power of these IEDs - they blow the lives of whole families apart."

The moderator designate studied chemical engineering at Strathclyde University before transferring to Glasgow University for a degree in divinity.

In the early 1980s he was a minister in Renton Trinity Parish in West Dunbartonshire, followed by Palmerston Place Church in the West End of Edinburgh.

A Kirk spokesman said these contrasting parishes gave him a "breadth of understanding of the challenges facing the Church".

Mr Chalmers, whose older sister June had Down's syndrome, supports the work of Enable and for 20 years he was a member of the Board of Donaldson's, the National School for the Deaf.

He was born in Bothwell, South Lanarkshire, attended Marr College in Troon and lives with his wife Liz in Dunfermline, Fife. The couple have three children and three grandchildren.