Other MPs do have extra jobs but I don't think it's appropriate to have two other jobs - one day a week and four days a week - which equate to a full-time post. If others are doing this, I think that is wrong as well. £75,000 per year deserves at least some commitment to the job.
He said that under his editorship the newspaper's principal objective is to represent London's interests. There is, I think understandably, a good deal of resentment about the constant focus on London, and this news will do nothing to dispel that. There is also, as has been mentioned, the conflict of interest regarding his job in the financial sector.
I think it's just greedy and unprincipled.