Can one mile take 10 years off your life?
In an interview in which he talked about inequality, Labour leadership candidate Sir Keir Starmer told BBC political editor Laura Kuenssberg: "Here in Somers Town, the life expectancy is 10 years less than a mile up the road."
Somers Town is an area of north London that includes King's Cross and St Pancras stations - the Office for National Statistics (ONS) calls the area Somers Town and St Pancras.
The most recent life-expectancy figures to go down to such small areas were for 2009-2013, when the life expectancy at birth for males in the area was 77.5 - for females it was 81.6.
The only area in London with male life expectancy 10 years higher than St Pancras and Somers Town is Knightsbridge and Belgravia, where the life expectancy for males at birth was 89.1 and for females it was 91.5.
The borders of the two areas are one and a half miles apart, so only a touch further than Sir Keir suggested.
We have contacted his office to check those were the areas he was referring to but have had no response.
Even closer than Knightsbridge is Holborn and Covent Garden, which is less than half a mile away and had female life expectancy of 90.2, although its male life expectancy was not much more than Somers Town at 79.4.
"If you look at data for bigger areas such as local authorities in London, the differences are smaller," says Veena Raleigh, senior fellow at health charity the King's Fund.
"But we are right to look at smaller areas because they pick up larger variations such as when you have one council estate with much higher levels of sickness and death than somewhere nearby."
It's not just London that has such variations. In Liverpool, for example, the ward of Kirkdale has life expectancy of 71.6 for males and 76.8 for females, while less than three miles down the road is Childwall with life expectancy for males of 83.1 and 85.9 for females.
There are other parts of London with striking differences in life expectancy over small areas.
This was highlighted at the time of the Grenfell Tower tragedy. The tower is in the area of Notting Barns, which had a life expectancy for males of 77.4 in 2009-13 and 85.5 for females.
Just over half a mile south of the tower is the area called Holland, where life expectancy at birth was 86.7 for males and 92.9 for females (the highest in London).
These figures are calculated over a five-year period to make them more robust but they are still very small areas to be calculating life expectancies for.
For example, while it gives the central figure of 77.5 for men in St Pancras and Somers Town, the ONS says it is 95% certain the actual figure is somewhere between 75.8 and 79.2.
Nonetheless, the differences we have been talking about are so large they are well outside the margin of error.
The data also includes figures for healthy life expectancy, which is the number of year's someone can expect to live in good health.
The inequality in this area is even greater. For St Pancras and Somers Town, both male and female healthy life expectancy at birth was 55 years, while in Knightsbridge and Belgravia it was 79.1 for males and 78.3 for females.
"That reflects a national position where differences in healthy life expectancy are about double the differences in life expectancy," Veena Raleigh told Reality Check.
"The differences in mortality are just the tip of the iceberg."