Perhaps. I note that position is being advertised by Oxford Knight, a high-touch recruitment firm. Their main modus operandi is to make contact with someone looking for a job, find out what they are looking for, and then suggest particular openings on their books to them; they would have plenty of opportunity to explain about the compensation. I think these public job listings are a bit of a cheap additional thing, and aren't that important to them.
I would recommend joining with some recruiters from Durlston Partners. They are fairly upfront about the compensation on offer and for C++ in London it is significantly better than the numbers I've seen in this HN thread. For example, I've seen roles with base salaries of £250k and generally large (or even uncapped) bonuses on top of this...
