Putative Western Lesser Black-backed Gull (Larus fuscus graellsii). It is the first of the two graellsii recorded so fare in Aarhus Harbor this summer and there is photos from its first day here.
Judged only on upper part colors we cannot safely dismiss an intergrade between intermedius and graellsii, but it is much paler than a classical Danish breeding intermedius.
It’s at least a 10th calendar year bird as it has been recorded annually in Aarhus Harbor since 2004 when it was in adult plumage, it's present annually from late summer until late autumn. There is an unread metal ring on its right tarsus and the legs are at maximum only slight yellowish in contrast to other adult Lesser Black-backed Gulls present making it easily identifiable from year to year.
Note that the putative Larus fuscus graellsii is in the upper left corner whereas an adult black-backed intermedius is in the right hand side.