By the way, Russia is a particularly bad choice. Russians are not permitted to work in London, it's outside of Europe and there is no immigration agreement. The resume won't survive the first pass from HR.
Remember that you're competing against 300 million Europeans who can move to and work in London overnight. You better have a great profile to be worth the hassle. Forget about low level roles and smaller companies.
Let's ignore for a minute that the parent was not Russian. Having a Russian number is a red flag that the candidate may be abroad and not have the right to work in the UK. It's definitely screened out by HR.
London is full of employed Russians so your information is perhaps outdated.