What is the secret John has hidden in the secret bunker build under the block off flats his parents left him?

What is the secret John has hidden in the secret bunker built under the block off flats his parents left him?

D.I Rawley, was insistent she wasn't to look around or she will be back with a search warrant  Problem is that won't happen ans she is going to be very pissed when then happens, it would be better if she didn't find that out.

I really couldn't see a way around it, it was starting to look as if one off her officers was not only a Mossad agent but had killed my date and framed me so he could get time in my flat to search it. He didn't know about the hidden bunker where all the documents were stored but he had torn the house up looking.

I was not concerned that she was going to find that  out but attempts to get a search warrant were going to make it a problem for me and she was going to keep banging away till she had an explanation, what to do maybe she should vanish but no that would alert Mossad.