Since Rugby Union turned professional this season and began to pay its players - previously strictly amateur - teams in the south have begun importing players from the northern professional League sides. As most come just for the season, there's no point in buying a house, so they are renting. And paying handsomely.
"The relocation of rugby players is big business for us," says Sophie Emerick, of estate agent Chestertons in Barnes. "It will be even bigger next year as more Rugby League players will be loaned from their union clubs."
Other estate agents are in a scrum to cash in. Many of their staff are involved in the game; the former England player Rob Andrew was a chartered surveyor with a top estate agency. Such employers allow time off for training because it's good for the company's profile.
Some London clubs, such as the Wasps, Saracens, Harlequins and Richmond, have had to find homes for their visiting players. All of which is music to the ears of property owners in the favoured areas. A one-bedroom flat near the club can command pounds 200 a week; two-bedroom homes pounds 350 and three-bedroom houses up to pounds 500 a week.
Before, it was just lucky owners near Wimbledon's lawn tennis club who bagged sports stars in need of a billet. Some paid their children's school fees, or flew off to Barbados on the proceeds. Now Barnes, Richmond and Twickenham are reaping the benefit of the collapse of the barrier between League and Union rugby. It's been likened to the demolition of the Berlin Wall.
Andy Challis, first team manager of NEC Harlequins, says: "As Rugby League now plays during the summer, the players can play for a union side until about February. Of course, they need somewhere to live, so we try to help as they don't know the area. I have been talking to estate agents and looking at houses. We like to put them in properties of a reasonable standard."
Harlequins has two League players currently on loan: New Zealander Robbie Paul, Rugby League player of the year, lent by Leeds; and Gary Connolly from Wigan.
Connolly had only five days to find a home before playing his debut match for the Harlequins. A bachelor, and happy to let Andy Challis make the choice, he found himself in a pretty little mews house in Barnes. Robbie Paul, with a girlfriend and two small children, viewed a few houses before choosing a three-bedroom house in Strawberry Hill, Twickenham.
"We are based at Twickenham, so Barnes is good as it's only about five miles away, and is also near to the Riverside Club in Chiswick where Gary trains," says Challis.
The players coming down from the north have been taken aback by the cost of renting.
"I couldn't believe the cost," says Antonia Seadon, Robbie's girlfriend. "The house we are staying in now would cost about pounds 400 a month in Bradford. Down here it's about four times that much. You pay pounds 1,500 a month for a little box. In this area, which is good, middle class, it's as good as you get. It's quite nice, but I have to admit we were shocked."
In Bradford, the couple own a three-bedroom semi. "Up there, you could have rented half a castle with eight bedrooms for pounds 500," adds Antonia.
Prices in the south were not such a surprise to Philippe Sella, the French rugby player currently turning out for the north London club Saracens. He and his family are renting a spacious flat overlooking Regent's Park, where charges are commonly pounds 1,000 a week. Or to Australian Michael Lynagh, also playing for Saracens and renting in Hampstead. Fellow Australian David Campesie is also reported ready to sign up to Saracens.
It could prove harder to persuade sportsmen and their families to relocate up north, though prices are much lower there. Footballers have had more experience in the relocation game. In 1966, when England won the World Cup, there were only 10 foreign players in the British league. Now there are more than 100. All the top London clubs have foreign players: West Ham has six, Chelsea has three Italians and a Dutchman.
But even the Brazilian, Emerson - signed to play for Middlesbrough for pounds 4m - had to take his homesick fiancee Andrea da Silva back to Brazil when she declared she couldn't cope with the North-east. "I was cold and I cried all night," she said. "I felt it was a strange, terrible place. I hope I never have to return."