Yes, in 1976. They didn't lock me up, but kept me at the police station while they took my boyfriend back to our flat and searched it. I waited in the room they took your photographs in, and chatted to a perfectly nice copper who thought it was total nonsense that he had to nick a pair of middle-class young people, with decent jobs etc, just because one of them had a tiny bit of hash.
They found our dope plants, and we both got done for cultivation of cannabis, as did our flatmate (he got done for possession, too).
When they came back, the nice copper asked me if I knew what the plants were. Given that there was a "grow your own dope" book on the living room table and a "legalise cannabis" poster on the stairs, I felt I could hardly deny it, so said yes. Both coppers rolled their eyes and I'm sure if I'd just said no, that would have been the end of it.
We all got a £50 fine (a huge amount of money then) for cultivation and BF and flatmate were fined £25 for possession as well.