Born: October 12, 1923;

Died: September 24, 2020.

DAVID Scarth Ritchie was the second of four remarkable siblings, who all survived the war and multiple life events, to live into their 80s and 90s. David was the last one standing.

He served during the war with the Royal Navy and was in Australia when the war with Japan ended in 1945. After being demobbed he worked as a weather forecaster, based not far from what is now Stansted Airport.

He joined Barr and Stroud in Glasgow, in 1948, working his way up from scientific instrument engineer to company director with responsibility for all research. At one point, he was in charge of a team of 600 technical staff. He invented a number of optical and electronic systems, some of which were patented. He brought some prototypes home and I can remember having fun in my pyjamas using a night-vision rangefinder to "spy" on the neighbours from our house in Helensburgh.

Although his primary work was with periscopes, he was also involved with the development of rangefinders and night-sights.

One invention addressed the problem of condensation on the glass viewing surface of periscopes as they changed temperature, passing from water to air. He had the idea of placing fine wires into the glass. A small current passed through the wires, creating heat and thus dispersing the condensation. This invention was commemorated in a scale model presented by the staff at his retirement and is similar to the equipment in most car rear-windscreens today.

After retiring in 1986, his subsequent roles included chairing a Scottish Education Department survey on industrial liaison, and becoming a governor at Paisley University and Visiting Professor in Management Technology Innovation at Strathclyde University.

My father was born in Edinburgh to Professor William and Madeline Ritchie. He was educated at The Edinburgh Academy, from Denham Green through the prep and senior school, leaving in 1941. He planned a career in medicine but had a last-minute change of mind and went to Cambridge to study mechanical sciences.

He got a rugby blue and captained the Corpus Christi side. Later in life, he played for a combined services side at Murrayfield and his father nearly had a heart attack with the emotion of supporting him in that game. Whilst in the officer training corps at Cambridge, he had to defend a bridge across the Cam, in case of invasion. A pontoon was built with the Royal Engineers to cross the Cam. It promptly sank.

After Cambridge, he joined the Royal Navy, training at Greenwich College. He served on HMS Berwick and HMS Newfoundland with the British Pacific Fleet in China, Japan (where he climbed Mount Fuji) and Australia as an Instructor Lieutenant.

In 1947 he married Heather McLennan, daughter of Brigadier K.A.T. McLennan, at St Giles Cathedral, Edinburgh. During the 1970s, David and Heather purchased a plot of land near Newbyth, East Lothian. It was not far from Prestonkirk, where they are both now buried, and was covered in silver birch trees and rhododendrons. They began the huge task of landscaping and created a wonderful garden. During the long wait for planning permission to build their retirement home, wonderful Sunday lunches were served from a caravan on the plot.

He was made an elder of Prestonkirk, East Linton, and worked on a number of projects including the transfer of the stained-glass windows from St Andrews church in East Linton. He was an active member of the East Linton History Society and Saltire Society.

Sadly, Heather died in 1987, aged 62. David struggled with life without her although he had the support of his large family. In 1988 he met Astrid Huggins (nee Chalmers Watson) in the lunch queue at a conference. They were married in 1989 and were together for 31 years.

With his and her houses in East Lothian and Ann Street, Edinburgh, they were well set and their combined talents and knowledge made them formidable dinner-party companions.

In 1987, he was approached by Sidney Ross to become a Trustee of the James Clerk Maxwell Foundation, which was formed in 1977 to honour and promote the memory and scientific contributions of James Clerk Maxwell, one of Scotland's most eminent physicists.

David filled many roles for the Foundation, showing great energy and dedication. In 1993, as Director of Development, he masterminded the raising of £500,000 to buy 14 India Street, a New Town house where Clerk Maxwell had been born. He worked tirelessly in writing hundreds of letters to individuals, trusts and charities to seek contributions. The funds were raised, thereby establishing Maxwell’s legacy in Edinburgh.

David was elected a Fellow of the Royal Society of Edinburgh in 1997. He donated a fine portrait of Clerk Maxwell which now hangs in the society’s Maxwell Room along with a hologram of the Maxwell statue, situated in George Street. In 1999 he founded the James Clerk Maxwell Cancer Research Fund with a group of oncologists.

He was an able watercolour artist and played the cello and piano. He is survived by Astrid, four children, two stepdaughters, 10 grandchildren, three step-grandchildren and 14 great-grandchildren.

Alastair W S Ritchie