Properties with access to gardens in Knightsbridge, Kensington and Chelsea are typically worth 20% more than those with no garden, estate agency Patterson Bowe said.

Gardens and roof terraces are in high demand across the SW3 and SW7 postcode areas and even access to a shared open space could boost a house price, the firm said.

Its research found garden squares alone could add as much as 15% to the final valuation. This compares with a 20% price boost for homes with a dedicated garden.

It said those properties without any outdoor space typically command around £80,000 to £100,000 less in today’s market than similar properties with outside space.

Stuart Patterson, managing director of Patterson Bowe, said with the city enjoying a warm summer the demand for outdoor space was reaching new highs.

“While the warmer months are upon us, Londoners who are fortunate enough to have their own outside space count their blessings,” he said.

“The benefits of London living combined with the luxury of outdoor space are both highly sought after and highly expensive. Property with private outdoor space is obviously the most desirable but even those with access to a communal garden square or proximity to a public green space can still add a surprising amount of value; especially in summer.”