I wonder what old Western knife fighter Jim Bowie (1796-1836) would have thought about modern majority non-white London, with its exciting knife culture?
  https://www.breitbart.com/europe/2019/04/07/khans-london-average-of-40-knife-crimes-every-day/

“A Freedom of Information request by the London Evening Standard has revealed there are an average of 40 knife related incidents every day in the British capital. The request revealed that in 2017 and 2018 there were a total of 29,232 knife related incidents reported, including 9,030 stabbings. The homicide rate involving knives was an average of one knife-related death every four days. The figures come as knife crime in London is at the “highest and most worrying” level in 40 years, according to London Metropolitan Police chief Cressida Dick. The area most responsible for the rise in crimes was the London borough of Southwark, with 1,594 offences occurring in the area. Southwark also reported the highest number of knife-related murders, with 17. Of 33 London boroughs, only Bexley was reported not to have had a single knife-related homicide over the previous two years. According to figures by the Office for National Statistics, in the year ending June 2018, there were 14,987 reported offences involving knives, a rise of 15 percent. This figure represents 38 percent of all knife crimes across England and Wales.”

     Clearly, the answer now is for Londoners to wear medieval full plate armour, while going about their business. Armour will need to be carefully constructed so that the blades are not able to get through gaps in the armour, which was a common problem in the medieval and later periods, where even though armour had become sword-proof, daggers still could be used up close to attack the gaps. But modern technology and material science may be now able to overcome this problem. The people of London will be relieved. Surely this is an easier solution than immigration control, something way beyond modern populations.