Most Euphorbias have very woody rootstocks. I would try some cuttings at this time of year before trying to divide. Although they bleed sap (wear gloves), some will root fairly easily.

The sap is a severe irritant and if you get it in your eyes you'll probably have to go to A&E and you'll suffer a lot of pain! Please wear gloves and take care if you are dealing with this plant.

thanks everyone, I do know about the sap, and I am very careful when removing stems.it is a beautiful plant, but it is too large for the area it is in, until someone can tell me that it is likely to survive dividing l will just carry on cutting out some stems.