You need to hit it with a hammer and a drift, preferably a copper
drift. I actually use a metal drift, a cut down rocker shaft, and a
good large hammer. I put the hub nut back on to the stub axle, after
you have removed the drum, not all the way, just to protect the
threads. In your case I guess you don't need to do that! If you are
renewing it, make sure the new one is exactly the same. There are a
few different ones in use. AFAIK Peugeot don't sell these, but Citroen
do. Always use a new nut and peen it to lock it.