yes with the ignition on and pump running fuel is entering the carb throat and were talking about stromburge carbs now.
I think that as fuel is being pushed out of the good carb's return pipe to a Y peice were the other (Bad Carb) is connected and and insted of the fuel being sent to the tank its taking the short and easy route into the bad carb return forceing fuel into the throat.

But if that is the case then i have followed how the Land rover manual shows and tell me how to plumb the fuel pipes.

could be wrong though.

And yes its the 17th21st Lancers Motto but the regiment is now The Queen's Royal Lancers.

OK, some progress with the description of the problem but unfortunately, that's me out now as I know stuff all about the Stromberg set up.....I was thinking in terms of SU's.

Just had a look at the book and an old manifold with Strombergs on it in my garage. I can see the pipe that you are talking about but I don't know what it does. In the book its described as a 'choke pipe'.

Sorry I can't help further and good luck.

Cheers

Chris

ps. My Grandfather was a 17th/21st 'Donkey Whalloper' in WW1. They did ride horses and carry a lance back then!