A lot of the confusion over breeds is caused by pet owners not understanding there are two separate breeds and regularly referring to cavaliers as "King Charles' spaniels. This is the most common term used in Ireland and I would guess the UK as well. In rescue I regularly got calls for people looking for 'a King Charles'. It is one reason I called the Irish rescue Irish CAVALIER Rescue but most people still ask for 'a King Charles' or ask for help rehoming their 'King Charles'. I have pretty much given up asking if they mean a King Charles or a Cavalier...

An 11 lb dog could be overweight dog even if it were a slightly undersized for a cavalier (not much -- in the UK/Ireland where the breed originates, breed standard is 12-18 lbs so a single pound under isn't particularly small). But am sure Polly is not fat going by your pics! My Tansy is small, around 10.5 or 11 lbs as well; at 12 to 13 lbs she would be overweight yet still on the smaller side for a cavalier. Judging a healthy weight depends entirely on the build of the individual dog and really has nothing to do with the pound or kilo weight in isolation. A 35lb cavalier might be perfectly fit and healthy while a 12 lb cavalier could be overweight -- each for its correct and healthy size.