I must be very good indeed at growing tasty broad beans. Well, certainly the local population of blackfly seem to agree. The autumn-sown Aquadulce Claudia escaped the onslaught - we had 3 harvests from them during May/June. But the spring-sown broad bean mixture have been plagued by them since they threw up their first shoots. I've tried the various remedies - squishing them (I can't bear doing it, even wearing gardening gloves), spraying with a soap solution (works to a certain extent but doesn't actually vanquish them all) and pinching out the leafy tops (they colonised too quickly along the entire height of each plant for that to have any effect).
So, though I'm loath to admit it, I've given up fighting. At least if they're on the broad beans then they're not infesting anything else in the suburban veg plot.