All,
I have noted the comments re AGM attendance above.
If you hold shares in certificated form, and have held for at least two weeks, there will be no problem, as they have a share register on the door.
If you don't, you need a letter from your broker confirming your holding, which can take a while to obtain. However, I normally take a screen print of my portfolio showing my holding in a stock as at the close of business the day before, and this has always been accepted as proof of ownership whenever I have done this.
In the worst case, you can ask to sign in as a guest, in which case you cannot vote, and they may leave you outside until the formal business has been conducted.