Peel the potatoes and cut into even sized pieces. Boil for 25 - 35 minutes or until soft. Drain. Mash in the milk, adding extra milk if necessary to make the potatoes smooth and creamy. Stir in the sundried tomatoes, oil and olives. Season with pepper.
The secret of good mashed potatoes is using floury potatoes. Some potato varieties which tend to be floury are - Ilam Hardy, Red Rascal, Agria, Fianna, White Delight. Look for bags in store which clearly show suitable useage. The closing tag will tell you the potato type.