It happened because people simply dropped in during recording sessions and were asked to join in. It is very unusual to have 27 musicians and singers on an album of traditional folk songs.
It was released in October 1971 on the Pegasus label. It was produced by Sandy Roberton and Ashley Hutchings (Shirley Collins' husband at the time). It was recorded at Sound Techniques, and Air Studios in London, in the summer of 1971. No Roses is an album by Shirley Collins and the Albion Country Band. Shirley Collins and The Albion Country Band