Really interesting thread; does anyone have an authoritative perspective on the deepest or/and earliest collection of folk songs from Romani, Gypsy and Traveller Communities in Britain?

Both Steve Roud (Folk Song in England) and Rob Young (Anthems in Eden) note Peter Kennedy's rich engagement with those communities in the 1950s as some of the most concerted undertaken, and Young also cites MacColl's (final?) radio ballad The Travelling People;

Roud also mentions John Clare in the 1820s, George Borrow in the mid-19th C, W.J. Ibbetson and Charlotte Sophia Burne in the 1880s, and then Lucy Broadwood and Ralph Vaughan Williams in the early 20th C (mainly around Gypsy wassailers).