The appointment was made by a panel of governors led by Lady Salisbury, which used an independent consultant to advise them on the process.
Malcolm Goodwin was first appointed to Capel Manor College in 2013 as an assistant principal. Over the last four years, he has been promoted twice, firstly as vice principal and then to deputy principal.
Lady Salisbury said: "The College attracted a strong field of appointments, but after a rigorous and detailed process, we feel very fortunate to have been able to appoint such a strong candidate. Governors believe that under Malcolm’s leadership, the College will go from strength to strength".
Goodwin said: "This is a very exciting time to be taking the helm at Capel Manor College. The College is in a very strong position with an excellent staff team and strong support from the land based sector in London.
"Capel Manor College is unique and a very special College that provides opportunities for the young and not-so young alike to get into the land based industries and a College that plays a vital role in the green agenda for London.
"I am looking forward to improving the opportunities and outcomes for students and supporting London’s needs for land based skills."
Dowbiggin said: "I have really enjoyed my 35 years at Capel Manor College.
"The staff, students and supporters I have worked with have made my time here relatively easy – it has been like conducting an orchestra which includes all the best musicians in the country.
"I am sad to be leaving, but this is the right time in my life to seek new challenges as the college is in the strongest possible position both academically and financially and with an excellent staff and reputation.
"Also, there are potential developments which will keep the new principal busy for the next 10 years.
"I am delighted the principal’s post attracted such a strong field of applicants. I believe it is one of the most interesting positions in the land based sector in England. However, I am also really pleased the governing body decided to appoint Malcolm. He has been a brilliant deputy principal and has the knowledge and experience to step up to the principal’s role and continue Capel Manor College’s exciting journey."