Ants as nectar thieves and pollinators

I've seen ants visiting small flowers before (like this one visiting sea milkwort) but I didn't notice the ant on this heath bedstraw until I knelt down to photograph the plant .....

..... it's just above and to the right of centre in the picture.

 On closer inspection it was clear that I wasn't just a casual visitor,,,,,

.... but was methodically moving from flower to flower, collecting something .... 

.... which I imagine was nectar rather than pollen. It might have been been transporting some pollen as it walked from flower to flower in the inflorescence but ants like this are unlikely to be very effective pollinators. 

The two-segmented waist indicates that this is an ant in the genus Myrmica.

At this point I had to beat a retreat, because its fellow ants had found their way up my trouser leg.