The pictures show a general view of my evergreen shrub, a close-up of one stem and a close-up of the flower. The foliage has a strong eucalyptus aroma when lightly rubbed with the fingers. It generally has two flowering periods in a season, May/Jun and Aug/Sep.

Is it one of the Australian mint bushes, Prostanthera rotundifolia?

Thanks for your suggestion. The Prostanthera rotundifolia is desribed as having purple flowers. As can be seen in the picture, the flowers are pure white with just a hint of purple inside. The leaves are almost of a succulent type and are small (approx 7-10mm) across and very tightly packed together.

Australian mint bush was right but its Prostranthera cuneata, commonly called the 'alpine mint bush', its lower and bushier than rotundifolia and i think a little hardier. best pruned back after flowering to keep bushy. personally I love the smell of P. rotundifolia and I'm not so keen on P. cuneata
best wishes, Lannerman