 He took over his father's supply business and developed it into Allnatt London Properties and other well-known businesses in England.Allnatt purchased Peter Paul Rubens' 1634 painting "Adoration of the Magi" for a record ₤275,000 in 1959 from the estate of the Duke of Westminster.Allnatt gave the painting to King's College in November 1961, and the painting was placed on permanent display in 1968 in the east end of the Chapel.