You haven't shown much foliage, nor told/shown us how high it is, but it looks like Phacelia, possibly P campanularia, hard to say without extra info.

Spooky - was just wondering if you were still on Goy - hadn't seen anything from you for ages. I am interested to know what this is - what a beautiful blue.

It's Phacelia campanularia, Cammomile - if its taller than about 6-8 inches, it'll be the same name but with the varietal name 'Blue Bonnet' added to it. Annual in this country.

Thanks very much for that Bamboo. I can see from the photo on Wikipedia that that is exactly what it is. Says it grows in desert regions so that suggests I should keep it fairly dry I guess. Very pretty flower. Having grown Phacelia tanacetifolia as a green manure and general plant for bees and insects for so long, I hadn't realised there were so many different species.

Such a lovely dark blue this one - all the other Phacelias are paler blue.

It's an annual most places, Bamboo. Here, where it's a native, it's a winter annual, so don't be surprised if it dies out during the hottest part of summer, Bertie. Easy to save the seeds, though, and easy to start. If the winter temps don't go much below -5º C, it might decide to seed itself, especially on sandy soil.