Rumours that Madonna's marriage is on the rocks have sparked conjecture on the division of her property portfolio - gossip that will not be go away despite talk of a reconciliation. This may be because, in a case of life imitating song titles, Madonna has secured her Material Girl reputation by making some unexpectedly good long-term gambles on the London market.

Madonna, pictured, owns two mansions in Great Cumberland Place, Marylebone, the first acquired in 2000, the one next-door in 2007; together they are worth at least £13 million. She is often snapped going from one house to the other - converted into a gym - as she was barred from knocking through. The bloomers she sports on these occasions are a less judicious choice than her location selection. Marylebone, although smart by any standards, used to be seen as the poor relation to Mayfair and Notting Hill. But it has now been classified as a prime area by Knight Frank. This bucks the nationwide trend for large falls in districts that were becoming gentrified by association, thanks to little more than their proximity to swisher, neighbouring areas.

Liam Bailey, Knight Frank's head of residential research, notes that, despite the slowdown, the price per square foot in Marylebone has climbed to £1,400, a large increase but still around half what a superstar mother and entourage would pay in adjoining Mayfair.

Factors behind the Marylebone boom include the gastronomic outlets of Marylebone High Street. These may not appeal much to Madonna (a Macrobiotic Girl) but a love of fine food is one common characteristic of people with money. Another is the desire to invest in a place that offers long-term value. More evidence of these instincts can be seen in the sales of expensive homes in Cornwall, now the land of Rick Stein's salmon escalopes.

Cash buyers are acquiring first and second homes inland or near to surfing beaches. The summer of 2008 is turning out to be a time when the position in the property market of those with ready money and those who need to borrow is akin to the gulf between a top recording artist and her fans.

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