Playing chivalrous Lord Grantham appears to have rubbed off on Hugh Bonneville, who was quick to open the door of his limo for new his flame – before diving into the car first when he spotted photographers.

The 60-year-old star of Downton Abbey and Paddington was seen last week with the vegan influencer on his arm a year after separating from his wife.

Wearing a stunning red dress with a plunging neckline, the Canadian was his guest at a cocktail party to celebrate the end of filming for the third Downton Abbey film.

It is the third time the couple have been seen together recently.

His new flame is Heidi Kadlecova who is a passionate vegan advocate on social media.

In March, the Bafta-nominated star was thought to be dating Canadian actress Claire Rankin, who was seen leaving his London flat several times. It now appears, however, that he has moved on from the 53-year-old.

Hugh Bonneville arrives with Heidi Kadlecova at the Downton Abbey cocktail

Divorced philanthropist Ms Kadlecova describes herself on social media as a ‘world traveller’ and ‘animal advocate’.

They first appeared in public together on July 8 at the premiere of the film Twisters, which stars Downton actor Harry Hadden-Paton. She wrote on his Instagram account: ‘Such a fun night and you are absolutely amazing in this film.’

Two weeks later she and Bonneville posted the same photo at the same time during the opening night of Fangirls, a new musical at the Lyric Theatre in Hammersmith, west London. A source told The Mail on Sunday at the time that ‘they gave themselves away at Fangirls’ and were ‘clearly sitting together’

Last week, the couple arrived at the Downton Abbey party at The Cross, a speakeasy-style bar in King’s Cross, around 8pm in a chauffeur-driven white BMW.

In a display of gallantry befitting Lord Grantham, when they left two hours later Bonneville went to open the car door for Ms Kadlecova – but swiftly ducked inside himself when he realised he was being photographed.

He has yet to divorce his wife of 25 years, Lulu Williams, 56. The couple, who lived in West Sussex and have a grown-up son, Felix, announced their separation last September. He reportedly joined the celebrity dating app Raya.

The star was thought to be dating Canadian actress Claire Rankin in March

Bonneville had referred to her as his ‘bedrock’ and ‘anchor’, but after they split, a source said: ‘Lulu feels as if 20-odd years of marriage counts for nothing.’

Ms Kadlecova has worked at non-governmental organisations in Uganda, Indonesia and Nepal. While married to lawyer Richard Coglon, they lived in Vancouver with their daughter, Gabrielle.

Her social media accounts suggest she believes meat and animal products are linked to diseases including cancer. She has also acted, playing a mother in Pintu, a 2016 film about domestic abuse.

Bonneville’s spokesman declined to comment last night.