 On 7 December 1207 he was elected to the see, and consecrated to it at Glasgow on 2 November 1208.In 1215, Walter was one of three Scottish bishops to attend the Fourth Lateran Council at Rome (the other two were William de Malveisin, bishop of St Andrews and Bricius, bishop of Moray).He returned to Rome in 1218, as part of a delegation of three Scottish bishops, including Bricius of Moray, and Adam, bishop of Caithness, in order to obtain absolution from Pope Honorius III for the sentence of excommunication imposed on King Alexander II and the whole Kingdom of Scotland.