David Randall helped research the sonic boom and in retirement bamboozled Ham&High readers with hundreds of cryptic crosswords.

The mathematics graduate from Imperial College London had an agile mind which became restless in retirement.

So Mr Randall, who lived in Muswell Hill and Finchley, wrote to Ham&High newspaper editor Matthew Lewin in the mid 1990s and suggested a tailor-made local crossword for the readers.

Mr Lewin took him up on the offer and for the next 15 years or so Mr Randall, who died this month aged 81, set about creating brain-teasing puzzles for readers based around local clues.

Son Lucian Randall, 40, said: “He would go up to his study and get onto Word every evening for a couple of hours and he would sit there with piles of dictionaries and books.

“But he would still need my help with a modern word now and again.

“He would work local things into the clues too.”

Lucian, who lives in Hampstead, has enduring memories of his father at the breakfast table pouring over a Guardian crossword.

It would be a rare morning for his father, a Ministry of Defence (MOD) employee for most of his life, to take more than 15 minutes to complete it.

Mr Randall’s intellectual ability saw him become the first member of his family to go to grammar school and university.

He moved to London in the 1970s after working in Farnborough for the Royal Aircraft Establishment looking at the effects of the sonic boom.

After finishing working for the MOD at 65-years-old, Mr Randall started jobbing on the Ham&High and wrote close to 800 cryptic crosswords during his time on the newspaper’s payroll.

“I think that generation of man, they had done a lot and he didn’t have that routine anymore,” said Lucian, his only son.

“But he was a great lover of words, classical music and was into politics and arts, so he was always out and about and loved walking in Hampstead and Kenwood.

“He was one of those chaps who didn’t want to sit around watching telly all day in his retirement.”

Mr Randall moved to Bournemouth in 2007 with his wife after becoming ill.

He was forced to give up crossword writing last year and died after a long illness.

He is survived by his wife Gloria and son Lucian.