Montgomery's mother died in 1937 while on holiday in Burnham-on-Sea after suffering from an infected insect bite which caused septicaemia following amputation of her leg.

[4] David attended Winchester College from May 1942 onwards, and his father, posted abroad from the middle of the year, arranged for his time in school holidays to be divided between his prep school headmaster and family friends, Major Thomas Reynolds and Mrs. Phyllis Reynolds, and Jocelyn, wife of David's half-brother John Carver, as well as strict instructions that "on no account" was the boy to visit his aged paternal grandmother, whom the then Sir Bernard Law Montgomery detested, in Inishowen, County Donegal, in Ulster.

[2] Montgomery entered business, working for Shell, Yardley and several other companies, and he built close links with Latin America.

He served as a patron and chairman of various Anglo-Latin American organisations, including the Anglo-Argentine Society, Canning House and the Hispanic and Luso Brazilian Council.

He also received decorations from Germany, Belgium, Spain, Chile, Argentina, Brazil, Mexico, Venezuela and Colombia.