A property sold for £5m more than its asking price after a bidding war – leading a buying agent to warn that selling agents’ pricing in parts of London “is all over the place” at the moment.

The unmodernised house in Holland Park went on the market with a well known national estate agent at around £13m – or around £2,500 per square foot. We have been asked not to name the selling agent.

A client of buying agent Black Brick was interested in the property, which is in an area where prices are down 15% from peak, and where agents and analysts are complaining of weak sentiment and low transaction volumes.

The client was outbid as a short bidding war and a round of sealed bids led to the property selling for over £18m – working out at £3,500 a square foot, which is thought to be a new record for the area.

Caspar Harvard-Walls, a partner at Black Brick, said: For really high quality, best in class properties, there is serious competition out there, partly because there are so few of them on the market. As with the Holland Park property, we’re seeing them change hands at record prices.

“Lower quality properties, on the other hand, aren’t moving and, in fact, many aren’t coming to the market at all. If vendors don’t need to sell, they’re renting them out instead.”

This poses particular challenges for buyers, Harvard-Walls continued. “It is very hard to work out where value is.

“Getting a sense of when a property is going to go off like a rocket is extremely difficult in this market. Pricing is all over the place.

“It’s very important that, when buyers get into a competitive bidding situation, they act rationally and calmly. It’s very easy to get massively carried away, and overpay for a property.”