Hello @adiroiban,
I understand your concern, I always found it strange for folks to question less known or free service entities. But accept every day general services without much investigation…
One could ask same question for banks, if you store XYZ $ what if their data center gets wiped. Your data gets lost, how do you prove anything? Obviously not.
Without knowing the stock share business, each business has certain compliance to meet. I presume that any business that wants to be sustainable and successful would adhere to thouse standards.
So in this specific query we have 2 3rd parties involved.
Bank which has segregated account where the free funds are protected. Which is Barclays bank.
Second entity is Interactive Broker’s which is custodian to your equity.
You can do some background on both institutions.
Other information you can read: