is this it:
Back in the 1960s I heard a tale about an Austrian Jew, John Brune, a friend of travellers who liked to sing their songs. When he was performing in Ewan MacColl and Peggy Seeger's Singers' Club in London and was in full traveller flow, Ewan had interrupted him demanding that, in future, he sing Austrian Jewish songs - it being the club's policy at the time that people sing only songs from the land or ideally the region of their birth. John, the story went, recorded himself singing a traveller song falsetto and sent it to Ewan, who then went out on a wild goose chase to look for this remarkable unknown traveller woman. I never knew the truth of the story, and was completely taken aback when Sheila began to explain why her voice never appeared on the Radio Ballad, 'The Travelling People'.

"Ewan MacColl had got a bee in his bonnet that there was one particular song that I had to learn, because he wanted me to open the programme and finish the programme. So he sent this wee Austrian man John Brune to teach me a song that had seemingly been collected from a Maggie Johnson down in England, but I had to sing it in an Irish style. And I said, 'Well I'm sorry John, but I cannae waste time, I'm at berrypicking, I need the money, I've got kids to raise.' 'That's quite all right.' he says, so he came out to the berryfields with me and he walked up and down the berryfields with me, teaching me this song, how to sing it. Then John went back, and two days before the programme was due to go out, he phoned Ewan MacColl and said, 'Ha ha, there never was a Maggie Johnson, it was me that made the song.' So Ewan panicked. The whole programme was made by this time so he had to miss me out and put in Joe Heaney (singing another song)!"