Interesting presentation of how Intelligence Agencies work, more or less this is how I would have expected them to work, thanks for confirmation.
I do have few doubts related to alleged Russian sources of information.
As Putin’s dictatorship is widely presented as extremely brutal to his opponents and quite good to his friends I would not expect anybody close enough to know such details to be tempted by anything that ex-MI6 agent could offer.
After all they had to risk their lives, what could they get in return that could tempt them?
Money? They have enough.
Power? They have more than most.
Maybe they were blackmailed by ex-MI6 agent? That sounds more plausible if the information they were blackmailed with would have them killed anyway. But British (even ex) agents don’t use these techniques, do they?