Artwork is copyrightable and for a known artist lasts for the artist's lifetime + 70 years from the calendar year in which the artist died.
He died in 1918 but may be best to check with either DACS or the Patent Office just to make sure you're not breaching anything:
DACS (Design and Artists Copyright Society)
www.dacs.co.uk /
[email protected]
Tel: +44 (0)20 7336 8811
Fax: +44 (0)20 7336 8822
The UK Patent Office
www.patent.gov.uk /
[email protected]
Tel: +44 (0)20 7596 6566
Fax: +44 (0)20 7596 6526