FREEK

This FREEK, and the others in extras, got me to down gardening tools and sit on the sea wall with a mug of tea for half an hour after I'd finished lopping off the flowers of all the yellow monsters.  

@Gladders gave me the name so I was able to find out that each plant would produce up to 2,000 seeds. Yikes!  Nothing else would have a chance to grow and seed heads were already forming.  Quickest solution was 'off with their heads.'  Then I started to dig them up by the roots as suggested by @Tivoli and @Arachne.  There are too many to do in one day but I dug up a few and found they came out of the sandy soil relatively easily.  

I might have been tempted to keep going but for the sight of these guys having fun.  I'm glad they were out.  They move so fast it was good fun trying to get them in the frame.  Wind's dropped now and they've gone.