It is sometimes difficult to think of something original to say about another yellow crucifer. This one grows in waste places, quite likes the seaside and is usually glabrous (bald). You might even think that as its name has the word Rocket in it, that you could use it in a salad. Indeed I have read this recommendation:

Diplotaxis muralis can be finely chopped and added sparingly to salads or used as a flavouring for cooked dishes. A piquant flavour, somewhat resembling rocket, Eruca sativa, but with a sharp aftertaste.

Warning: Don't try it. It's other common name is Stinkweed and you'll know why if you crush a leaf and take an deep sniff. I find that many (but not all) people on whom I inflict this experience respond with the word Bleeeaaerrgh! often followed by expletives and accusations of attempted poisoning. To me it has a nauseously disgusting smell much worse than the crushed leaves of Stachys sylvatica (Hedge Woundwort) for instance. The smell is useful for identification as only plants of this family smell like this but none quite so bad as Diplotaxis muralis.

You can find it along most of the coastal stretches of England, Wales and South Eastern Scotland but it is quite common inland in England as well. Records diminish as you go from southern to mid Scotland and from there northwards it is uncommon. It is found in Ireland mostly in the east.