What a very strange looking beastie was the aesthetically unappealing Heyford! I am guessing that this was the predominant RAF night bomber at this time (1935), replacing the last Vickers Virginias in the Home RAF, when that force was made up almost entirely of biplanes. Its unusual configuration was practical in some ways, but it must also have been an on-going physical challenge to the people having to service them, as well as the aircrew members attempting to reach their "work stations"!
David D