Dennis was born on 7 November 1929 in Gillingham, Kent. Evacuated to Llantrisant in Wales during the war, he had a lifelong love of Wales.
He did his National Service in the Navy, and went on to study for a degree in Engineering at the University of Newcastle upon Tyne.
After university, Dennis joined the Ministry of Defence and spent his working life touring Britain's naval ports. He worked for the Admiralty in Chatham, Rosyth, Bath, Plymouth and Chatham again. Later, Chatham Dockyard was closed and he worked as a Technical Manager and Consultant for English Estates, who took over Chatham Dockyard.
For the last two and a half years of his life he lived in Pembroke House, the retirement home run by the Royal Navy Benevolent Trust. He died on 1 May 2018, aged 88 years.