Mazars broke down which postcodes saw the most ‘risky’ mortgages in the last 12 months, which is defined as a home loan where the sum borrowed is worth at least 4.5 times the salary of the borrower.

Previous analysis from Mazars has found that more than 86,000 of these mortgages were written in the 12 months to the end of March, with a total value of around £30.6bn.

This latest study pinpoints the specific postcodes where these mortgages have been most prevalent, with London dominating.

The area with the highest value of risky mortgages is Wandsworth, where £232m of such mortgages were written. It was followed by Battersea, Wimbledon, Fulham and Tooting.

In fact, each of the top 10 were found within London, while 19 of the top 20 postcodes with the most risky mortgages were located in the capital. The sole exception was Maidenhead in Berkshire, which is itself still a popular area for commuters.

Mazars said that there may be concerns that lenders are concentrating too much of their risk within a small geographic area, with rising arrears and repossessions likely to disproportionately impact the ‘risky’ borrowers.

However, Paul Rouse, partner at Mazars, suggested that lenders will feel these areas are likely to see demand remain strong even in the event of a recession.

Rouse said lenders have to make a “very careful judgement” about where they write these sorts of loans, and they “clearly see south London as a sensible place to do that”.

He continued: “Hopefully the concentration of such a large amount of their lending to their most highly-geared customers in an area about 20 miles wide will only get challenged by the bank’s own stress testing.

“With the housing market potentially facing further choppy waters in the coming months, mortgage lenders will be hoping that their loan books are well-prepared to weather some defaults.”