I am a UK9, 53cm calf, 5'10" tall. These look lovely, very smart, but the ankles were really baggy, and the foot was really wide too. My foot just slipped right out.
The description says they will fit 45-53cm calves, but I could get them round mine when the straps were fully closed so I'd say the capacity is much bigger than that.
Having said that, I think they were a little short for me, and perhaps weren't hitting my calves at their widest point.
I have bought the Navy "hard wearing" boots instead. The fit around the foot and ankle is MUCH better, and still plenty of room round the calf.