Bastard Cabbage - Rapistrum rugosum

An annual crucifer, casual on arable and waste ground; usually roughly hairy and with lobed leaves and light yellow flowers.  The fruits are variable, but very distinctive.  They are in two parts; the lower part is usually oval and the outer (distal) part is larger, rounded and ribbed, abruptly narrowing into the style. 

When not in fruit, this can be mistaken for other yellow-flowered crucifers. The seed pods are the best identification feature.

Photos of whole plant and detail of ripe seedpods

Arable and waste ground

summer and autumn

Frequent and increasing; can become locally common and invasive

Few records