An overwhelming number of responses to my post, thanks to all of you, much appreciate your interest, especially to you Sandra. Unfortunate however that most of the responsive interest was focussed on John's ancestors and of life from his birth in Canada to the end of WW2. My post had however, called for any information of his existence post 1949. I have his entire life documented prior to 1949, all thanks to my friendship with John's granddaughter here in Australia where we both live. We had a person-to-person meeting just last Saturday in Perth, her mother (JR as mentioned by you Sandra) still lives in Essex in England. Her mother is still mystified as to her father John's 'disappearance' post 1949, and as Sandra did indicate, he was not present at her wedding in April 1960. She (JR) the eldest of 5 siblings. A sixth child, a daughter died in 1945 aged 8.
The following summarises deployment of John Allen's then regiment 13th/18th Hussars post WW2. John could have been part of that deployment. He was clearly a career soldier.
The regiment was posted to Northampton Barracks in Wolfenbüttel in March 1946 and returned to the United Kingdom to its new base at Willems Barracks in Aldershot Garrison in October 1947. It was deployed to Libya in February 1948, to Egypt in April 1950 and to Malaya, for service as an armoured car regiment during the Malayan Emergency, in June 1950. It returned to Wolfenbüttel in November 1953 and then moved to McLeod Barracks at Neumünster in April 1956 from where it deployed a squadron to Aden. It returned to Malaya and was posted to Ramillies Camp at Ipoh in July 1958. I have found no reference to their deploying troops during the Korean War 1950-1953. A military discharge and/or death of John are the missing pieces of his data. Note: Cornwall's population includes more Allens and Allans than anywhere else. I have Allen ancestors of Cornwall. It's far too easy to assume that a John Duncan ALLAN's (note spelling) death recorded at Liskeard in 1976 is our quarry. Most unlikely.