There are a lot of gaps in 17th century winning horse names. Often mares names were left out, or the horse name referred to the owner. King Charles' winning horses in 1671 and 1675 weren't named I think
http://www.highflyer..../royalplatesnotes.htm
thanks to you both. I have trawled through google, and found that in 1675 he probably won on Blewcap, but can find no trace of a horse beginning with W. ( Unless there is an error in the question ) and the articles you quote dont actually state that he won the Newmarket Plate on Old Rowley in 1671. Thanks again for trying.