I believe this question has been asked before and no-one seems to know. Shazam fails to recognise it, my guess it's a library piece of some sort or a specially commissioned piece of music in which case only ITV will have it.
As a general rule if Shazam and friends dunno what it is, then its not commercial - either it'll be library or an original commission. There may be exceptions - I have noticed music that originally appeared in video games seems to occasionally be used on some shows, it happened last week on The Apprentice where I immediately recognised a piece of music that first appeared in The Sims.