Boris Johnson’s father and reported partner were among protesters at an event opposing Japan’s plans to resume commercial whaling.
Stanley Johnson and ocean conservationist Carrie Symonds, who is reported to be Boris’s girlfriend, were speakers at the anti-whaling protest in central London on Saturday.
Japan took the decision in December to leave the International Whaling Commission, and this week Japanese whalers were discussing plans to start commercial hunting along the north-eastern coasts for the first time in three decades.
Mr Johnson and Ms Symonds were spotted smiling and chatting together after they both addressed the crowd.
Speaking to the Press Association beforehand, Ms Symonds said: “I think that whaling is incredibly cruel. There’s no two ways about it. And the main reason often given for whaling is that it’s tradition.
“But I think that this is the kind of tradition that should remain in the dustbin of history.
“Quite frankly we’ve all seen the pictures of whales being slowly killed with the sea turning red with blood as they’re harpooned.
“It’s violent. It’s disgusting. And these are some of the most endangered and intelligent and beautiful creatures we have.”
She added: “How about we start a new tradition today? And instead we have a tradition where we protect these animals, we respect these animals and we recognise how lucky we are to live alongside these animals.”
When asked whether Boris Johnson would be joining her at the protest she declined to comment.