This species is the very common Grypocoris stysi, which is often found on umbellifer flower heads, like the hogweed below.
I think this little green species, which turns up on many plants in our garden, is possibly the common green capsid Lygocoris pabulinus, but there are several rather similar small green capsid bugs so I could be wrong.
You can see the typical capsid proboscis here, which can penetrate plant tissues, the bodies of small insects and even human skin in some of the larger bug species, like water boatmen.
I thought this species, which took up residence on the dill plants in our garden, would be easy to identify because of that yellow chevron marking - but there are several similar species that are described as 'very variable' in their markings, so Liocoris tripustulatus is not much more than a guess at an identification.
You can find a picture of a more colourful species by clicking here.