MOMBASA — Bethan, 56, lives in southern England on the same street as best friend Allie, 64.
They are on their first holiday to Kenya, a country they say is "just full of big young boys who like us older girls".
Hard figures are difficult to come by, but local people on the coast estimate that as many as one in five single women visiting from rich countries are in search of sex.
Allie and Bethan -- who both declined to give their full names -- said they planned to spend a whole month touring Kenya's palm-fringed beaches. They would do well to avoid the country's tourism officials.
"It's not evil," said Jake Grieves-Cook, chairman of the Kenya Tourist Board, when asked about the practice of older rich women travelling for sex with young Kenyan men.
"But it's certainly something we frown upon."
Also, the health risks are stark in a country with an AIDS prevalence of 6.9 per cent. Although condom use can only be guessed at, Julia Davidson, an academic at Nottingham University who writes on sex tourism, said that in the course of her research she had met women who shunned condoms -- finding them too "businesslike" for their exotic fantasies.
The white beaches of the Indian Ocean coast stretched before the friends as they both walked arm-in-arm with young African men, Allie resting her white haired-head on the shoulder of her companion, a six-foot-four 23-year-old from the Maasai tribe.
He wore new sunglasses he said were a gift from her.
"We both get something we want -- where's the negative?" Allie asked in a bar later, nursing a strong, golden cocktail.
She was still wearing her bikini top, having just pulled on a pair of jeans and a necklace of traditional African beads.
Bethan sipped the same local drink: a powerful mix of honey, fresh limes and vodka known locally as "Dawa", or "medicine".
She kept one eye on her date -- a 20-year-old playing pool, a red bandana tying back dreadlocks and new-looking sports shoes on his feet.
He looked up and came to join her at the table, kissing her, then collecting more coins for the pool game.
Mr. Grieves-Cook and many hotel managers say they are doing all they can to discourage the practice of older women picking up local boys, arguing it is far from the type of tourism they want to encourage in the east African nation.
"The head of a local hoteliers' association told me they have begun taking measures -- like refusing guests who want to change from a single to a double room," Mr. Grieves-Cook said.
"It's about trying to make those guests feel as uncomfortable as possible ... but it's a fine line. We are 100 per cent against anything illegal, such as prostitution. But it's different with something like this -- it's just unwholesome."
"One type of sex tourist attracted the other," said one manager at a shorefront bar on Mombasa's Bamburi beach.
"Old white guys have always come for the younger girls and boys, preying on their poverty ... but these old women followed ... they never push the legal age limits, they seem happy just doing what is sneered at in their countries."
Experts say some thrive on the social status and financial power that comes from taking much poorer, younger lovers.
"This is what is sold to tourists by tourism companies -- a kind of return to a colonial past, where white women are served, serviced, and pampered by black minions," said Nottinghan University's Davidson.
Many of the visitors are on the lookout for men like Joseph.
Flashing a dazzling smile and built like an Olympic basketball star, the 22-year-old said he has slept with more than 100 white women, most of them 30 years his senior.
"When I go into the clubs, those are the only women I look for now," he said. "I get to live like the rich mzungus (white people) who come here from rich countries, staying in the best hotels and just having my fun."
At one club, a group of about 25 dancing men -- most of them Joseph look-alikes -- edge closer and closer to a crowd of more than a dozen white women, all in their autumn years.
"It's not love, obviously. I didn't come here looking for a husband," Bethan said over a pounding beat from the speakers.
"It's a social arrangement. I buy him a nice shirt and we go out for dinner. For as long as he stays with me he doesn't pay for anything, and I get what I want -- a good time. How is that different from a man buying a young girl dinner?"