Johnston's proclamation of a further protectorate, the Nyasaland Districts Protectorate, west of Lake Malawi was also contrary to Foreign Office instructions. However, it was endorsed by the Foreign Office in May 1891. This was because the discovery of the Chinde channel in the Zambezi delta, which was deep enough to allow sea-going ships to enter the Zambezi, which was an international waterway, without having to enter Portuguese territory, whereas previously such ships had to use the port of Quelimane. Salisbury was also influenced by the offer by the British South Africa Company to fund the administration of the protectorate, which convinced him to bow to popular pressure. There followed an Anglo-Portuguese Crisis in which a British refusal of arbitration was followed by the 1890 British Ultimatum of 11 January 1890. This demanded that the Portuguese give up all claims to territories beyond the Ruo River and west of Lake Malawi. The Portuguese government accepted under duress and ordered their troops in the Shire valley to withdraw to the south bank of the Ruo. This order was received by the commander at Katunga on 8 March 1890 and all Portuguese forces had evacuated Katunga and Chiromo by 12 March.