New thriller inspired by the UK's most notorious heist

After an enforced break (caused by house renovation and garden design – not my favourite occupations) from writing and book promotion, I am climbing back into the saddle. There is still one major agent looking at 'The Immortality Plot' and follow-up book 'Good Girl Bad Girl' but, although he requested the MS and said he would endeavour to get back to me as soon as he could that was back in early May.
It's hard to know if he has no interest or is so impressed he is passing the books around his agency to garner support.
I understand when a agent just doesn't bother to reply to an initial query. That usually means not interested but when the agent clearly is and takes forever to come back with a decision it kind of leaves you in limbo.
By book promotion activities just nosedived but I am planning a new Kindle Countdown deal for three books I wrote many years ago and I have just got back into blogging and social networking a little. I'm still not convinced it does much good. Visibility or lack of it is the goal of all self-published authors but this is becoming harder and harder to achieve given the sheer volume of titles out there.
So, I am writing a new thriller, this time set in the UK (for the first time). In Harry Chance, I've created a protagonist who is on the wrong side of the law and becomes embroiled in the internecine war that followed a real life and most notorious gold bullion heist. Although factual, the story behind the heist reads like a Lee Child thriller. In today/s money, the bullion haul would be worth a cool £90 million. And a large proportion of the gold has never been recovered.
The bad guys are still looking for it and so are the police. Someone made off with the bullion under the noses of the ringleaders.
And they think it was Harry Chance.
But was it?