Menus should mark meals containing allergens with a red 'A', a coroner has said, after a teenager died from eating a chicken burger he didn't know contained buttermilk.

Owen Carey, 18, suffered a fatal allergic reaction and collapsed in front of the London Eye after dining at the O2 Arena Greenwich branch of restaurant chain Byron in April 2017.

Mr Carey, who had a dairy allergy, did not realise that the skinny grilled chicken burger he had ordered contained buttermilk, as he enjoyed a family dinner to celebrate his birthday.

The sixth form student, from Crowborough, East Sussex, tragically passed away hours later after being taken to St Thomas' Hospital in London.

An inquest into his death at Southwark Coroner's Court today heard that Byron's menu did not indicate that the item had been marinaded in buttermilk.

Assistant Coroner Briony Ballard said introducing a "simple red A" next to menu items which potentially contain an allergen could help "prevent future deaths".

Questioning Aimee Leitner-Hopps, Byron's head of food and compliance, Ms Ballard asked: "Why don't you put a big A beside all of the dishes that potentially contain an allergen? I don't understand the problem with that."

Ms Leitner-Hopps, who denies any wrongdoing by the firm, said customers should inform staff if they have any allergies.