I think he got the lyric fragment from the Bod. Quoted in the notes to 'Unearthed', (Mollie Music MMCD02/03) Nic writes:

Described on the broadsheet as 'A new song - Buonaparte's escape from Russia', I added a few extra words, wrote a tune and called it 'The Warlike Lads of Russia'. This recording was originally on a compilation album the late Fred Woods brought out called 'The First Folk Review'. It subsequently featured on the compilation album 'Flash Company', recently reissued by Fellside in celebration of their 25th aniversary.