Contract changed because of terms in an "Employee handbook"

[smax]

Hi, 9 years ago I joined my current employer. My contract states I may be paid a discretionary bonus, which "is conditional upon the Employee remaining in the Bank's continuous employment for a further 6 months from the Discretionary Bonus Payment Date". A year or two after joining we were all told this 6 months was being increased to 1 year and we had to acknowledge this by email response. When I queried what appeared to me to be an enforced contract change with my manager at the time I was told that the contract says we have to obey the employee handbook and this is what was changed. The contract also states that the bonus needs to be repaid less tax.
I'm now approaching retirement and I was paid a bonus in April this year (which I have already spent), and am wondering about my options. Talking to colleagues I've been told that it is not whether you leave within 1 year, but whether you resign within 1 year. As I have a 3 month notice period, this is significant difference - I would need to wait until next April before I can resign otherwise I'd have to pay this money back.
I'd like to ask the HR department but I know from my last manager that if you do so, they immediately contact your manager and tell them you are about to resign. I don't want my manager to know my resignation plans as I haven't made my mind up yet. I have tried looking on the firm's internet for the employee handbook (I'd also like to confirm whether I need to repay tax too as this may have changed also) but cannot find it.
It seems rather unfair to me that I have to reveal my plans to the company just to see what has been changed in my contract.
Thanks in advance for any help.

[ULA]

Can you post up the full clause in your employment contract containing the details of the bonus. Make sure anything that can identify you or the company is anonymised

[smax]

This is what the original contract I signed says:

The Discretionary Bonus, if any, is intended to keep the Employee motivated and incentivised and is conditional upon the Employee remaining in the Bank's continuous employment for a further six months from the Discretionary Bonus Payment Date of the year in which the Discretionary Bonus, if any, is paid (the "Discretionary Bonus Retention Expiry Date")

although I have no idea what the Employee handbook says.

[ULA]

It would seem that you need to refer to the staff handbook. This should be a readily available document to all staff normally these days via a company intranet or shared staff access drive. If not there should be no reason why you cannot ask HR for a copy without referencing what part you are specifically interested in.