boundary between Alfred's and Guthrum's kingdoms was to run up the River Thames to the River Lea, follow the Lea to its source (near Luton), from there extend in a straight line to Bedford, and from Bedford follow the River Ouse to Watling Street. Alfred succeeded to Ceolwulf's kingdom consisting of western Mercia, and Guthrum incorporated the eastern part of Mercia into an enlarged Kingdom of East Anglia (henceforward known as the Danelaw). By terms of the treaty, moreover, Alfred was to have control over the Mercian city of London and its mints—at least for the time being. In 825, the Anglo-Saxon Chronicle had recorded that the people of Essex, Sussex, Kent and Surrey surrendered to Egbert, Alfred's grandfather. From then until the arrival of the Great Heathen Army, Essex had formed part of Wessex. After the foundation of Danelaw, it appears that some of Essex would have been ceded to the Danes, but how much is not clear. 880s With the signing of the Treaty of Alfred and Guthrum, an event most commonly held to have taken place around 880 when Guthrum's people began settling East Anglia, Guthrum was neutralised as a threat. The Viking army, which had stayed at Fulham during the winter of 878–879, sailed for Ghent and was active on the continent from 879 to 892. There were local raids on the coast of Wessex throughout the 880s. In 882, Alfred fought a small sea battle against four Danish ships. Two of the ships were destroyed, and the others surrendered. This was one of four sea battles recorded in the Anglo-Saxon Chronicle, three of which involved Alfred. Similar small skirmishes with independent Viking raiders would have occurred for much of the period as they had for decades. In 883, Pope Marinus exempted the Saxon quarter in Rome from taxation, probably in return for Alfred's promise to send alms annually to Rome, which may be the origin of the medieval tax called Peter's Pence. The pope sent gifts to Alfred, including what was reputed to be a piece of the True Cross. After the signing of the treaty with Guthrum, Alfred was spared any large-scale conflicts for some time. Despite this relative peace, the king was forced to deal with a number of Danish raids and incursions. Among these was a raid in Kent, an allied kingdom in South East England, during the year 885, which was