The eight-year-old pair, Yang Guang (Sunshine) and Tian Tian (Sweetie) were put together one last time before the female bear’s annual window of fertility ends.

“Natural sparks” flew between the pair – on loan from a Chinese Zoo – yesterday, but they didn’t mate.

Keepers opened a “love tunnel” between their enclosures after tests showed Tian Tian had ovulated.

They are kept in separate enclosures because pandas are solitary by nature and experts believe that if they live together they could form a sibling-like relationship and not breed.

They were put together for five minutes at a time, until the female became “fed up”, and both pandas slept between the conjugal visits.

Female pandas are only fertile for 36 hours a year and a spokesman said the pair’s flirtatious behaviour of their first few encounters was gone.

Zookeepers said the couplings were difficult for the bears because they were both sexually inexperienced.

Iain Valentine, director of research and conservation at the zoo, said: “Each time the pair met we saw a huge amount of eagerness and attraction between Tian Tian and Yang Guang.

“There was lots of vocalisation and encouragement from our female and physical contact between the two. He mounted her several times, however full mating did not occur.

“Although both have bred before and have borne cubs with other pandas, they are both still relatively inexperienced. At the end of the day, this is year one of a 10-year conservation project here at Edinburgh Zoo.

“We are hugely encouraged by how much the natural sparks flew between the two animals, as like humans, not all male and female pandas are attracted to each other.”

Darren McGarry, head of animals at Edinburgh Zoo, said: “We certainly had the foreplay, we just didn’t get them on to the next stage.”

Two older giant pandas in a Japan zoo mated this week after spending three days together in the same pen, raising hopes for baby cubs in the summer.