London does have a large population of rats, but the actual figure cannot be known nor can we say for sure that there are six rats to every person.
According to Dr Stephen Battersby, who has researched British rat infestation for decades says there are maybe 10m rats. However, Dr David Cowan suggested there are 1.5m rats in total in Britain but says it's impossible to know for sure and urges caution at jumping to conclusions.
Rats have been large in number in Britain but there is not enough credible evidence is available to verify that the rat to person ratio in London is six to one.
Correction: A previous version of this fact-check stated this claim to be Unverifiable. This was incorrect. This is Partly True as London does have a high population of rats, but it is not possible to assess the exact number in comparison with people.