It was the first small taste of freedom for Bobby the 23-year-old silverback gorilla since he was captured as a baby in Guinea and sold to an Italian circus.

He can now see the sky without bars and, from today, thousands of visitors to London Zoo can look him and his fellow great apes in the face.

Removing the gorilla cages is the biggest revamp at the zoo for 40 years and is intended to turn a visit into something more akin to a safari park experience.

The island habitat is part of an African rainforest area and the gorillas can be observed from a forest glade, or bai. Visitors can walk along raised paths and view the gorillas across a moat fitted with electric fencing to prevent any escapes.

The £5.3 million Gorilla Kingdom could also become a simian version of Celebrity Love Island and pull in the crowds to watch the mating antics of a gorilla ménage à trois.

Conservationists are desperate for Bobby to sire a young gorilla. He has been a toy boy for Zaire, 32, for four years but she is now too old to breed, has lost a few teeth and has a swollen belly. Now a younger, slender model has arrived from Leipzig, Germany.

Effie, 14, and Bobby have started to make contact but she will not move in with Bobby and Zaire until the relationship is on a firmer footing.

Daniel Simmonds, a keeper, said: “We are taking the courtship gently. It started with an hour a day; now it is three hours. It is going well and they have already started touching each other. They do naturally fight and squabble with each other but we do not want it getting out of hand.

“We also have a bit of a problem with Zaire, who is getting jealous of her love rival. We are convinced they will soon settle down and live as gorilla groups do in the wild. When a young gorilla comes along, Zaire will make a good aunt. Older females help the mothers to rear the young.”

Another two females will soon join the community. The eventual plan is to replicate a colony of western lowland gorillas living in the wild and to provide Bobby with a harem. The 6,000 sq m area includes hills, waterfalls and caves and is big enough for eight gorillas.

The BBC is in negotiations to place a webcam at the site. Zaire is particularly fond of gardening and spends some of her day moving plants.

The Duke of Edinburgh, opening the exhibit yesterday, wanted to hear all about the love triangle.

When the Duke began to speak, Ellie was clearly interested and clambered right up to the glass.

Keepers had heated rocks on the island and left out bananas to tempt Bobby close to the thick glass screen, but he chose to keep his distance.

Big facts

— Gorillas are the largest primates in the world and share 98 per cent of their genes with humans

— The three main species in Africa face a very high risk of extinction. They are under pressure from habitat loss, the bushmeat trade and disease

— About 1,000 live in zoos around the world

— The longest recorded lifespan for a gorilla in captivity is 54 years

— Gorillas spend 40 per cent of their time resting, 30 per cent feeding and 30 per cent travelling or playing

— Gorillas can walk upright but rarely do — they prefer to walk on all fours

— They produce 25 distinct noises from hooting to grunts, screams and barks

— In the wild they eat leaves, shoots, stalks, stems and vines, bark, fruit and termites. At London Zoo they drink 6 to 8 litres a day of herbal tea, and are also partial to popcorn Source: Zoological Society of London

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