Hi Steve,
This is "Ymdaith Gwyr Dyfnaint" - which translates as 'The March of the Men of Devon'. A great tune indeed! As far as I know it is traditional Welsh and a written version can be found in
'Blodau'r Grug' - 100 Popular Welsh Folk Dance Tunes, published by the Welsh Folk Dance Society. In that book it is paired with 'Machynlleth' (see below), another really stonking Welsh processional tune to make up the dance set 'Ffaniglen'.
Cheers,
Steve
Machynlleth - Welsh traditional march/processional
X:1
T:Machynlleth
M:2/4
L:1/16
C:Traditional
R:Processional
K:G
P:A
|:dedc BcBA|G2G2 G2AB|c2A2 A2A2|c2A2 A2Bc|
dedc BcBA|G2G2 G2AB|c2A2 G2F2|G4 G4:|
P:B
|:FAcA FAcA|GBdB GBdB|FAcA FAcA |FAcA GBdg|
e2e2 e2g2|d2d2 d2g2|d2c2 B2A2|G4 G4:|
P:C
|:d3e d2c2|B4 B2c2|d3g f2e2|e2d2 d4|
d3e d2c2|B4 B2d2|c2A2 G2F2|G4 G4:|
P:D
|:A2AB c2A2|Bcde d4|A2AB c2A2|Bcde d4|
e2e2 e2g2|d2d2 d2g2|d2c2 B2A2|G4 G4:|