There's also the story from Geoffrey of Monmouth (c.
1136), who says that Gormund, the 'King of the Africans', invaded Ireland and Britain and was allied with the Saxons against the Britons. Some people have suggested that Gormund was a Vandal king.
Chapter 8. Britain, in the flame of a civil war under king Careticus, is miserably wasted by the Saxons and Africans.
"After Malgo succeeded Careticus, a lover of civil war, and hateful to God and to the Britons. The Saxons, discovering his fickle disposition, went to Ireland for Gormund, king of the Africans, who had arrived there with a very great fleet, and had subdued that country. From thence, at their traitorous instigation, he sailed over into Britain, which the perfidious Saxons in one part, in another the Britons by their continual wars among themselves were wholly laying waste. Entering therefore into alliance with the Saxons, he made war upon king Careticus, and after several battles fought, drove him from city to city, till at length he forced him to Cirecester, and there besieged him. Here Isembard, the nephew of Lewis, king of the Franks, came and made a league of amity with him, and out of respect to him renounced the Christian faith, on condition that he would assist him to gain the kingdom of Gaul from his uncle, by whom, he said, he was forcibly and unjustly expelled out of it. At last, after taking and burning the city, he had another fight with Careticus, and made him flee beyond the Severn into Wales. He then made an utter devastation of the country, set fire to the adjacent cities, and continued these outrages until he had almost burned up the whole surface of the island from the one sea to the other; so that the tillage was everywhere destroyed, and a general destruction made of the husbandmen and clergy, with fire and sword. This terrible calamity caused the rest to flee whithersoever they had any hopes of safety."
Geoffrey of Monmouth - History of the Kings of Britain, p.195
https://www.yorku.ca/inpar/geoffrey_thompson.pdf