Alyssum saxatilis 'Dudley Neville' now Aurinia saxatilis

Lovely creamy yellow flowers smother this compact mound of grey-green leaves, will spill down a wall or bank from mid spring until frosts. Hardy and easy, but I have found it to be not so long lived on occasions, but prop cuttings into sand to preserve and share. Trim to maintain shape in winter. Rock garden trough, sand and gravel gardens.  Full sun. up to 60cmW 30cm H so three times larger than the species. 

www.gardenerspath.com has some great information on this and many other plants,  and a wonderful image