I was going to say have a look at the IONIA at:
viewtopic.php?f=67&t=13566because she is the current ST. MAWES.
Your photo, however, looks to be the previous tug of that name.
ST.MAWES (IMO 5306435), Falmouth Towage Co Ltd., 346gt,
completed Robb, Leith, 10-1951
1951 ARUSHA - 1959 ST.MAWES - BU Oosterschelde 17.1.84 [M.van der Marel]
Ron