Potatoes - when to harvest?

Hi guys! Well my potatoes are growing quite wildly now and starting to flower. My question is, when ideally can I harvest some. I've got 4 different types on the go (one in each grow bag) so don't want to pick them all at the same type. Can I start harvesting a few after the flowers die off on the first bag? Advice much appreciated! :gnthb:

 

As soon as the flowers start to look past their best you will have some small tatties in there. The trick is to not lift the whole plant, but shove your hand in and have a grope about, picking off just a few spuds at a time as you need them. A couple of weeks after your flowers have died off, the spuds will start to get quite large. That's the time to harvest them all I reckon, as you don't want to let them get too big because they lose all their flavour.