Oil trader gave £300,000 to Britain Stronger in Europe.
24 members of Downing Street staff were tipped for honours by David Cameron, but the office mouser was not mentioned.
Cameron's resignation honours list a way of "paying off a debt of support" says MP
'The public wants cleaner politics,' Cameron said after becoming Tory leader
About David Cameron
David Cameron took office in 2010 after forming a coalition government with Nick Clegg. He has since seen the popularity of his party fall as well as internal rebellions against the alliance with the Lib Dems.