Passage: A partial evacuation of British citizens was completed by 17 January, when the army riots in Southeast Africa prompted Rhyl's diversion to Tanganyika so the troops she was carrying could assist in quelling the mutiny. In replacement, a company of the Gordon Highlanders was loaded aboard Owen so an intervention could still be made if necessary. The aircraft carriers Centaur and Victorious were also transferred to the region as part of Operation Parthenon. Although never enacted, Parthenon was intended as a precaution should Okello or the Umma party radicals attempt to seize power from the more moderate ASP. In addition to the two carriers, the plan involved three destroyers, Owen, 13 helicopters, 21 transport and reconnaissance aircraft, the second battalion of the Scots Guards, 45 Commando of the Royal Marines and one company of the second battalion of the Parachute Regiment. The island of Unguja, and its airport, were to be seized by parachute and helicopter assault, followed up by the occupation of Pemba. Parthenon would have been the largest British airborne and amphibious operation since the Suez Crisis.Following the revelation that the revolutionaries may have received communist bloc training, Operation Parthenon was replaced by Operation Boris. This called for a parachute assault on Unguja from Kenya, but was later abandoned due to poor security in Kenya and the Kenyan government's opposition to the use of its airfields. Instead Operation Finery was drawn up, which would involve a helicopter assault by Royal Marines from HMS Bulwark, a commando carrier then stationed in the Middle East. As Bulwark was outside the region, Finery's launch would require 14 days' notice, so in the event that a more immediate response was necessary, suitable forces were placed on 24 hours' notice to launch a smaller scale operation to protect British citizens.With the merger of Tanganyika and Zanzibar on 23 April, there were concerns that the Umma Party would stage a coup; Operation Shed was designed to provide for...

Question: What did the incomplete evacuation end?
17 January