One in five flat owners made a loss selling their property last year, compared to just 4pc of detached house sellers. Demand for flats plummeted as buyers shunned cramped city living. Owners who sold in 2021 made an average gross gain of £54,690, down from £62,360 in 2020. 

In London, the average profit also fell as price growth remained sluggish. But past soaring values meant that the average vendor made a 58pc profit, equal to £197,730, the highest in the country. 

Typically, the longer a seller has owned a property, the bigger the gain when they put it back on the market. The average seller who bought 20 years ago enjoyed a 180pc increase in the value of their property last year, compared to 23pc for homeowners who bought five years ago.  

Aneisha Beveridge, of Hamptons, said: “Most of these profits are never seen by sellers as they are reinvested back into the housing market when they make their next purchase.

“House price gains last year were close to their peak, so if the average seller last year originally bought in 2012, they have benefitted from house prices across England and Wales having risen by 55pc in that time.”