I’m grateful to Jevgenia Milne for connecting us with the following great information about this really useful plant.
A member of the borage family like other comferys and alkanets it produces copious green manure and has edible flowers which are good bee fodder (and yes it’s quite invasive). We knew it was eaten in Turkey but had been struggling to find out how. This link gives detailed information. Plants readily available from the nursery!