This is the claim made by the TaxPayers' Alliance. The group, dedicated to "campaigning for lower taxes and better government", has divined this sum by taking Home Office and police data on the economic and social costs of crime, then factoring in criminal justice system bills and adding "security measures, physical and emotional costs."

Dividing this total - some £3bn - by the number of residents in each borough resulted in an area-by-area breakdown. Thus, while £400 might be the city-wide average, it seems that not all residents suffer equally. By the TPA's reckoning, folk in Westminster fork out the most, at £620 per person, while Richmond-upon-Thames residents pay just £215 per person.

While the maths might not be squeaky-clean, it's certainly a novel approach. According to official stats the rate of crime in London is dropping, but the public remains convinced that this is mere fudging and spin from the powers that be, and it is in fact on the rise. Knowing how much it hurts the wallet will doubtless fuel this theory.

With the topic a key plank of the manifestos of all three leading mayoral candidates, this unorthodox approach to quantifying the cost of crime to an individual's pocket may offer up a few choice soundbites between now and May 1st.

Yellow sign courtesy of west_end_ted's Flickrstream