Disembarking at Southampton

I'm taking a TA crossing from NY to Hamburg, stopping in Southampton.

If I want to leave the ship at Southampton for the day, do I need to disembark with all the other passengers who are not continuing on to Hamburg (in other words, do I need to wait for a special disembarkation time), or is there another gangway for those who are are continuing on?

Do passengers go through immigration after they disembark, or is it done prior to leaving the ship?

I can't answer all of your questions but immigration officers travel on board and immigration checks are done during the voyage.

Once you arrive at Southampton you are free to leave the ship without further checks.

Hattie pretty much summed it up. Immigration is done on board before you arrive. You can disembark for your Southampton exploration at your leisure. And I can add that you will use the same exit as those who are leaving the ship.

Thanks, Hattie & @tv24:

In Martin & Jan's blog, Martin mentioned another gangway exit for those visiting Sydney versus those disembarking Sydney in his blog, which is what prompted my question.

Thanks for your responses!