Met Police figures (not the Daily Mail's) show there have been 74 murders in London so far in 2018 (6 months) - of those 47 have been (obviously) fatal stabbings. Can't find stats for how many non fatal ones.
Knife crime in London does seem to be out of control - approx 25% up on 2017 whilst Met Police numbers have dropped to their lowest level since 1996.
Note I am not suggesting that other UK cities are not also blighted.