Additional grounds in support of the theory have been deduced from a tablet in the British Museum, which is dated in "the year in which the Amurru drove out Libit-Ishtar."[33] We have already seen, from information supplied by the Nippur dynastic list, that with Libit-Ishtar, the fifth king of the Dynasty of Isin, the family of Ishbi-Ura, its founder, came to an end, and that with Ur-Ninib a new family was established on the throne. By identifying Libit-Ishtar, the king, with the personage mentioned in the date-formula, it would follow that he lost his throne in consequence of an invasion of the Amurru, or Western Semites, who drove him from the city. But presumably they were at once dislodged by Ur-Ninib, who retook the city and established his own family upon the throne. According to this view, the supposed invasion was but an advance wave of the racial movement that was eventually to overwhelm the whole of Babylonia. Some thirty-three years later, in the reign of Bûr-Sin, Ur-Ninib's son, the Western Semites are represented as again invading the country, and, although this time they do not penetrate to Isin, they succeed in establishing a dynasty of their own at Babylon. But there are difficulties in the way of accepting this further development of the original theory. In the first place, it will have been noticed that no title follows the name of Libit-Ishtar in the date-formula already cited, and there is no particular reason why this not uncommon name should be identified with the king of Isin. It has further been pointed out that another tablet in the British Museum,[34] of about the same period, contains a reference to a Libit-Ishtar who was certainly not the king of Isin, but appears to have occupied the important post of governor of a provincial city, probably Sippar.[35] The writer of this tablet recounts how he had been imprisoned and had appealed to Libit-Ishtar to try his case and set him free; but he was met with a refusal, and he afterwards made a similar appeal to Amananu, to whom he ascribes the title of governor. In this passage Libit-Ishtar has no title, but since appeals in legal cases could be referred to him, he may very probably have held the same office as Amananu, that of governor of the city. In certain contract-tablets of Apil-Sin's reign a Libit-Ishtar is also mentioned in the place of honour at the head of the lists of witnesses, and he too should probably be identified with the same official. We may therefore conclude that the Libit-Ishtar in the date-formula served as the local governor of Sippar in the time of Apil-Sin, until he was driven out by the Amurru. Whether the Amurru are here to be regarded as the inhabitants of a neighbouring town,[36] or as a fresh wave of Western Semites, does not affect the point at issue. Since the Libit-Ishtar who was driven out was not the king of Isin, the arguments deduced from the tablet for the overlapping of the dynasties of Isin and of Babylon no longer apply.