How do I clean scuff marks off of white walls?

Without ruining the paint.

I've tried using a sponge with washing up liquid but that seems to just spread the dirt around.

Sorry if that was a dumb question. I've never lived in a home with white walls before and I'm not very domestic.

JML Magic Erasers. You can get the or something similar at Robert Dyas.

I would just try an ordinary eraser first, that seems to get a lot of things off. 

Thanks. I had to Google as I had never heard of erasers for cleaning before.

I will see if I can find some in a nearby shop.

Magic Erasers rock! I use them for everything

Limousine companies use WD40 to clean their white walls. They should know the best material.

Would anyone know which shops sell erasers and where I might find them? (What would be next to them.)

I tried to order from the Robert Dyas website but they are out of stock.

The home/gardening/DIY shop near me doesn't have them.

I am also near Homebase, Morrison's and Sainsbury's.

Do you mean regular erasers or magic erasers?

Regular erasers are at any stationers like WH Smith or Rymans. I got a magic eraser from Amazon.

I meant both.

Thanks.

Wet a white towel with a little water and rub gently.  It has always worked for me.