Though after the death of Drusus Tiberius appeared less frequently in public, he still conducted business in the Senate, and even after he had definitely withdrawn from Rome occasionally appeared in the vicinity of the city. In the year 27 A.D. a temporary wooden theatre, constructed by a speculator at Fidenæ, not far outside the walls of Rome, collapsed, involving in its ruins no less than twenty-five thousand persons. This disaster was almost immediately followed by a fire on the Cælian Hill, a crowded quarter of Rome. On both occasions the Emperor gave lavish assistance from his private purse, and promoted measures likely to prevent the recurrence of such catastrophes. He continued to transact the business which appertained to what we should call the Foreign Office of the Empire, and on all important occasions communicated with the Senate by letter, showing in such communications, at least up to the year 31 A.D., no abatement of his former ability; but he did, in fact, withdraw his attention from the details of government, and allowed the conduct of the legal processes in the Senate to pass into the hands of Sejanus. Sejanus, so far as we can learn from our authorities, took advantage of the increasing aversion of the Emperor from public affairs to take his place, to promote his own favourites, and gradually to occupy even in the eyes of the Prætorians that position which really belonged to Tiberius. It is possible that his procedure in the Senate was more autocratic than that of the Emperor. The situation was complicated by the continuance of the domestic rivalries of the Imperial household, which, on the death of the aged Livia in 29 A.D., broke out into a series of horrors whose exact nature cannot from want of evidence be determined, though it may be surmised.