The Emperor of Japan's state visit ended yesterday with a declaration by his official spokesman that it had been ''a successful celebration'' - despite being dogged by bitter protests.

Emperor Akihito himself looked highly pleased - after the part-time marine biologist saw a British collection of the goby fish he studies. The trip to London Zoo's aquarium ended four days of public appearances, many of which have attracted jeering and chanting demonstrators.

As the visit ended, the Emperor's press secretary for the visit said: ''I think the demonstrations paradoxically have cemented our relations.''

Kazuo Chiba said he did not agree with those who believed the state visit had been counter-productive, reopening old wounds resulting from the death and suffering of so many in Japanese war camps. ''I think it was paradoxical that it focused the attention of the British public in an unprecedented way on the visit,'' he said.