Asked if he thought his son, Boris Johnson, could become the next Prime Minister in the wake of a Brexit vote, Stanley Johnson replied he would be happy if anyone in his family is considered to have done a "useful job".
The chairman of Environmentalists For Europe who supports a remain vote, was campaigning in Bicester alongside Green Party MP Caroline Lucas, and former acting Labour leader Harriet Harman.
Mr Johnson also praised David Cameron's visit to Rainham Marshes Nature Reserve and statement on protecting the habitats of birds. However, Ms Lucas pointed out that should the UK vote to Leave the EU, Mr Cameron may no longer be Prime Minister.
With hours to go before polling opens, a ComRes poll for ITV News suggests nearly one in five voters haven't decided which way they'll vote.
Gary Lineker received a torrent of abuse on Twitter after revealing he is backing Remain in the EU referendum.
Michael Gove has apologised for his "clumsy" comments comparing EU referendum experts to Nazis.