This surpassed all expectations, turning into one of the best days we had in London. Our guide arrived promptly at our hotel, and from the moment we left, he provided a wealth of information on the passing sights and Windsor Castle. Once at Windsor he personally escorted us through security and got us situated on the grounds. (There are no personal tours inside Windsor Castle, so we were on our own, but it was all explained beforehand,) We swapped phone numbers and agreed on a meeting time outside the exit gate. It could not have been easier or more enjoyable.
I highly recommend this particular tour company as you are likely to have the owner himself as your guide, as we did. The personal service and overall experience, five stars and more!