Rocket?

Rocket?

Observation - Rocket?. Description: This plant has popped up at the bottom of my paddock - well away from any cultivation. The leaves have short spines to the edges and underside of veins, and the flower buds are also spiny. There are no pods or fruits. The leaves taste pleasant, a bit like

This plant has popped up at the bottom of my paddock - well away from any cultivation. The leaves have short spines to the edges and underside of veins, and the flower buds are also spiny. There are no pods or fruits. The leaves taste pleasant, a bit like sorrel. It reminds me of rocket, but doesn't match the descriptions in the books.