A row over lunch between two lionesses almost upstaged the Queen as she unveiled a new enclosure at London Zoo.

Accompanied by the Duke of Edinburgh, she unveiled a plaque at the Land Of The Lions exhibit, which will be the playground of four endangered Asiatic lions.

The Queen and Philip listened to speeches from Zoological Society of London (ZSL) president Sir John Beddington and director Ralph Armond, while lions prowled metres behind them in search of meat.

Professor David Field, zoological director at ZSL, said the argument which interrupted the opening ceremony was between five-year-old twins Heidi and Indi.

He joked that Heidi's growl "could have been a comment on the president's speech" but was more likely "an expression of delight at having the Queen and Philip back again".

He said: "The Queen kept taking a look at what the lions were doing behind them - especially when the lions were growling.

"And that's the beauty of it, because you're so intimate and so close with the lions you just don't quite know how close they are to you.

"They certainly took a little check to see what was happening."

Another zoo worker added: "Heidi is notoriously vocal. She likes to assert her authority. It's quite a dramatic sound if you're not used to it."

The Queen would have seen the two lionesses' grandmother, Ruchi, when she visited in 1976, Prof Field said,

She was presented with a photograph of that visit 40 years ago when she opened the New Lion Terraces at almost the same spot.

Dame Vivien Duffield and her daughter Arabella were in that photograph and were also at Thursday's launch.

"You look a bit different", the Queen joked to Arabella, who was just four years old when the photo was taken, prompting laughter from the crowd.

Dame Vivien said the Queen looked "fantastic" as they were reunited 40 years on.

Standing with her daughter the 69-year-old said: "I don't remember much about it 40 years ago but of course it was lovely.

"It was a beautiful ceremony and it's wonderful that she's here and looking so fantastic.

"And the lions are free now, which is rather wonderful."

Arabella, 44, said she was too young to remember seeing the Queen in 1976, adding that she now brings her two young children, Daniel and Alexander, to the zoo "all the time".

The family outing saw the royal pair stroll around the enclosure and meet the ZSL exhibit delivery team, zoo keepers and conservation group members.

The Queen wore a pale blue outfit and hat by Angela Kelly, which she last wore at the beacon lightings for VE Day in Windsor last May.

Philip was given a reproduction of a painting by Edward Lear circa 1835 of an Asian lion to accompany the publication, The Maneless Lion Of Gujarat.

Colourful murals of lions and monkeys decorated the old brick walls surrounding the enclosure, while a bright yellow cow with turquoise hooves and horns and floral decoration proudly guarded the entrance.

Guests were served mango bucks fizz with an edible flower and tea in keeping with the Indian theme, while Gitanjali Bhattacharya, conservation programme manager at ZSL, wore a pink and orange sari braided with gold.

A sign warned visitors not to cross the boundary fence due to "dangerous lions, dangerous ruins".

BBC Springwatch presenters Chris Packham and Bill Oddie attended the unveiling, along with hundreds of guests.

Praising the display, Packham said: "The wire they've got there is virtually translucent - you can just see right through it.

"You're only three metres away from a very powerful predator.

"They've done a great job."

The presenter joked that he would prefer to bed down in one of ZSL's overnight lodges overlooking the lion enclosure than stay at the Ritz.