 Denis Garrett akaberekwa muna 1906 paLeiston, Suffolk, kuna Mary née Marples, kubva kumhuri yeSheffield inogadzira maturusi, naStephen Garrett 18781915, director mubhizinesi remhuri yekurima michina muLeiston, Richard Garrett Sons. Aiva dangwe pavana vana. Baba vake vakaurawa muhondo paNeuve Chapellepanguva yeHondo Yenyika Yokutanga paakanga ava nemakore masere, uye amai vake vakatamisa mhuri kuOxford, uko hanzvadzi yake yaigara, uye gare gare kuEastbourne. Garrett akapinda Chikoro cheDragon muOxford, uye kwenguva pfupi Wellington College, kubva kwaakatiza, uye Eastbourne College, kwaakafarira biology yezvirimwa, kunyangwe paine kushomeka kwemakirasi ehupenyu, pamwe nemasvomhu. 