At least that is what we used to call it as kids. Now of course I know it is the product of a Common Froghopper nymph. The nymphs suck the sap of the plant to feed and also produce this froth to hide them from predators. They are widespread throughout the country and common on roadside verges, where I spotted this one.
In the morning Clickychick had been to see a client and then mid afternoon we headed into town. CC had spotted some young stock in a field so we detoured in case I could get a blip.
Typical cantankerous cattle they were nowhere near the gate where she had seen them so they were out as a blip. While walking back to the car I took a few shots of the roadside plants. Then I spotted the "Cuckoo Spit".