Cowderoy was born in Sidcup, Kent, on 5 May 1905 and ordained a priest in Southwark on 30 May 1931 by Peter Emmanuel Amigo.

[5] In recently revealed archives it is shown that in 1957 Cowderoy took a hardline approach from a Dutch priest and future Vatican Cardinal Johannes Willebrands to come and speak on ecumenism in his diocese.

"[6] In 1968 he took a hard line on the controversial papal encyclical Humanae Vitae and disciplined a young priest in his diocese was called the document on artifical birth control "regrettable".

Cowderoy's position was in contrast to the more moderate approsach of his fellow London Archbishop, John Heenan (cardinal).

[7] He was Grand Prior for England and Wales of the Knights of the Order of the Holy Sepulchre of Jerusalem.