.... In my experience, Most Definitely YES.
Just a few months ago a neighbor had a 10 - 15 year old (purchased just over a year ago, deliberatly looked like crap) GT STREAMLINE "Beater Bike" stolen off the street in City Center, (popped into a food court mickey D's for a quick bite, 30 min later, cablelock laying on the sidewalk) beautiful bright So. Cal. day. Cut a 15mm range cable lock, with the plastic coating was approx.18mm. One Clean Cut!!!

Hopefully you have been able to channel the anticipation and positive energy of finally taking delivery of your "Bad Boy" (by the way, Congratulations!!) into the "Due Diligence" and knowledge you will need to keep it from "Going Walkies".
You've made a good start by joining these forums.

I assume, that by now you have also joined lfgss forum and posed your very valid concerns to them, sifted through their various theft/security related threads, as well as picked the brains of the l.b.s. (local bike seller) where you purchased your theft target... Errr .. Bad Boy, for the best "Retention Strategies".
Hint: lfgss has for many years recommended TWO (2) high quality U/D locks (best practice: BOTH are ANCHORING the frame, front and rear wheels, to Separate Secure Objects) for London's mean streets, cable/rope Based locks serving as TERTIARY security At BEST.

Make No Mistake, You have a Brand New High Value Bike in a City that has the reputation of being the "Big Apple" of Europe re: Bike Theft. You must bring your 'A' Game, Best Practice is Your Best Chance!

In my opinion, YOU face an Extremely Steep Learning Slope in à very unforgiving environment, exacerbated by the fact that as a Commuter, by definition, means YOUR bike Will Be In The Same Area, LIKE CLOCKWORK FOR SEVERAL HOURS/ENTIRE BUSINESS DAY. Your best defense is to climb the curve as Quickly As Possible.
I sincerly wish you the Very Best Of Luck, May The Bike Gods Smile Upon You.
P.S. Should tragedy strike, Remember to Take Deep Breaths, Repeating to Youself, "This Is A Challenging But Valuable, Growth Opportunity. Challenging but Valuable Growth Opportunity. ChallengingButValueableGrowthOpportunity, challengingbutvalueablegrowthopportunity