Rupert Callender was moved to become an undertaker through his experience of bereavement and its aftermath. He spent much of his childhood in the hospice where his mother worked, and the caring, humanistic philosophy of the hospice movement is central to his work. He opened the Green Funeral Company with Claire in 2000, and the company is now among the country's best-known eco-friendly funeral directors; in 2012 they won Joint Best Funeral Director at the first Good Funeral Awards and were described as 'The best undertakers of all time, by a country mile' by Good Funeral Guide author, Charles Cowling. In 2021 Claire left the company and Rupert continues with a new colleague.

Callender, Phillips, Cauty & Drummond, Undertakers to the Underworld was established as a partnership between the Green Funeral Company and (The Justified Ancients of Mu Mu (KLF) in 2017.