Money has been stolen from my account?

It's more likely that you've spent it or a co-signatory to the account has, and you haven't been keeping an accurate track of what you've been spending. If you had £45k in the account and you spent £15-£20k on starting a business etc, you'd have £25k - £30k left (not £28k-£30k), less any other expenditure. You are alleging that someone in HSBC has committed fraud. Have you made a formal complaint to the bank and/or Financial Ombudsman Service or the Police? If you are 100% confident that you haven't spent the money, then that is what you should do. If the bank 'won't help' make a Subject Access Request under the Data Protection Act and request your statements and copies of transaction details since January (although if you are running a business, you really should have all this yourself), and compare it with your recollection. Identify the 'suspicious' transactions and question them with your bank. Although, due to the banking crisis, it's de rigeur to call banks crooks, they are regulated and as a rule, don't just help themselves to your money. There must be an explanation. It's highly unlikely that they will have done this to you and your fiance when theft from banks is quite rare - as a proportion of the number of transactions and accounts processed every day. The fact that you think that this has happened to your fiance leads me to believe that you, and your fiance, just didn't keep real tabs on what you have been spending and are delusional about your spending habits. I wish you well, however. You wouldn't be the first to have underestimated how much you've spent though!

Checking the statements should show you what money you have spent and what transactions you have not authorised. When you have identified the rogue transactions you can challenge the bank to provide details of them

Look at all your statements over the past 9 months. When, where & in what form did these payments go missing, are they cash withdrawals, what can you account for, are they debit card payments, where these made in stores or online, if so when to what company, can you account for these. You'll need to act fast though. HSBC should have a telephone banking system call them for any more info and you can process a complaint about your own branch at that point who have obviously been very unhelpful. If you haveb een in posession of your card the whole time then it's possible your card has been cloned. You can claim this money back, maybe not all of it as some banks only look at cases from the past 6 months but you may be able to claim something on top of that if you're branch has been inconsiderate of their customer needs. Keep track of phonecalls, visits to the branch, dates times and who you spoke to in the future. Contact them as soon as possible!

I suggest contacting the FSA.