George Spicer never sang Searching for Lambs. He had a song called Searching for Young Lambs (Roud 1437. Laws O9) which he did indeed record for Kennedy in 1956, and again for Mike Yates in 1972. However, while this is a pastoral idyll, very like SFL, it is an entirely diferent song.

The only field recording of SFL (Roud 576) I could trace is the one by Edwin Thomas. I've got some recordings of Edwin Thomas, including SFL, but I'm damned if I can remember what he sounded like. If I can find the tape I'll have a listen.

However, while the song snatch is too brief and indistinct to concoct any theories on, I couldn't say that it sounds particularly like a traditional singer to me.

Also, the Thomas recording was made 3 May 1952. If the film in question came out that same year, that doesn't leave much time for the recording to be catalogued and for the director to discover it, get permission to use it, incorporate it into the film and release it. (Having said that, I looked up Rotten Tomatoes, which is probably the best source of film data on the Internet. According to them it was released in 1953.)

Also, as far as I know, the version which everybody sings was collected by Sharp and Karpeles from Mrs Sweet of Somerton, Somerset, and the performance in The Long Memory has the same tune.

I'll know more when I can locate the tape, and hear the Edwin Thomas tune, but my guess is that the snatch we hear was rcorded by some prototypical folk revivalist, perhaps someone who was working on the set of the film.

Does any more of the song occur anywhere else in the film?