Aurinia saxatilis (often confusingly called Alyssum) is nothing like the common Alyssum (Lobularia maritima) found in so many pots and borders, though it is from the same plant family Brassicaceae.
Madwort is another common name and it is a delightful perennial that is perfect for rockeries as it forms a low mat and spills over edges like surf on a bright summer's day.
However as it's other common name infers (Basket of Gold), it is generally seen in yellow, even a bright golden yellow.
The simple four petalled flowers have stamen that spray upwards, making a very pretty display as they tend to produce masses of flowers in spring and early summer, so much so that they appear as a carpet of either gold or white..