There are several reasons you may not be seeing the male swan.

Sometimes, not always, but sometimes, male swans will take a break from the immediate area while the female is nesting. Are you absolutely sure that the swan you are seeing is not the male? If the female is on the nest and in a secluded area, you will only see one swan (the male unless he goes to the nest and allows the female to rest, bathe and feed). If the male was chased by a predator, he may have led the predator away and is not returning yet to insure that the predator does not return or because he was shaken from the encounter. If he was chased for some distance, he may have gotten lost and may or may not return.

If he was severely injured, he may not be able to return. If he was attacked and killed, he obviously will not return.

We are not sure how far you are located from Datchet, UK., but you might check with your local RSPCA or the swan rescue facility Swan Support in Datchet, to see if your swan may have been rescued. If he was rescued for whatever reason, they try to return the swans back to the area they were captured. So, this might be a possible source of inquiry for you. The Regal Swan