I do not doubt that the painting was done by hand - actually, I have no idea. However, it seems possible that the pattern/picture was purchased by Windsor and then reproduced, perhaps by multiple artists by hand. Here is an attachment of the picture earlier referenced as 'Silent Ships'. I took a screen shot b/c that was the only way I could share it.
You can see the signature on the lower left corner. It does not look like Edita, which led me to the above conclusion.