You can purchase the tool here for.....wait....wait.....hold on to your skirt.....$320

OTC Tools LRT-51-008 Pinion Flange Remover

 

Take a look at this post on Discoweb.
2000 DII pinion seal - DiscoWeb Message Boards

 

I don't have an exact measurment but probably almost 2".

 

GULP.................................$320 bucks eerrrr that's £200.................I think a bit of home made ingenuity is called for instead. 3" diameter steel pipe socket, some 3/8" plate and a 10mm high tensile 8.8 studding and matching nuts and washers. It's got to be worth a try and a lot cheaper.

What about hiring it from an LR shop?

 

There are some cheaper places to get them...but not by much. Here is how PTSchram on Discoweb says he removes them and he has removed plenty.

"The hole is 8*1.25.

I use my hub nut socket, a bolt and a washer. They have always popped right off for me, but some folks have a horrible time with them"

Maybe using an impact wrench as well....not sure.