He gained a Cambridge MA in natural sciences and an Imperial College PhD, before working for the next 16 years as a horticultural training officer, visiting nurseries and garden centres encouraging and training apprentices and managers.
He moved on to become a technical adviser at the HTA in 1991 - a role that took him up and down the country, meaning there are not many garden centres that he did not visit to give advice.
Because of his technical botanical knowledge, McKinley also wrote a book about poisonous plants. The garden centre labels advising "harmful if eaten" stem from his work.
As a minister, he served in the Southampton and Bournemouth circuits.