Although Great Britain has good relations with the Jewish state, it insists that the latter has only “de-facto authority over West Jerusalem.” Thus London’s embassy is in Tel Aviv, even as the seat of the Israeli government is in Jerusalem. Stephen Daisley laments this situation:
As recently as 2016, Foreign Office briefing documents were still referring to Jerusalem as corpus separatum. (You know your foreign policy has really kept up with the times when it requires a working knowledge of Latin.) Jerusalem was designated a corpus separatum in the 1947 Partition Plan for Palestine, which was adopted by the UN General Assembly, accepted by the Jews, and rejected by the Arabs, who went on to launch a war for “the elimination of the Jewish state.” You can see why the Foreign Office would consider this a totally reasonable and unproblematic basis for UK policy on the Middle East.
Originally, corpus separatum meant Jerusalem would be run by the United Nations. These days Israel wouldn’t trust the UN to run a shawarma stand, and rightly so. So corpus separatum, as used by the UK government, has come to mean split sovereignty in Jerusalem, with Israel controlling the western parts of the city and a future state of Palestine the eastern portions. Curiously enough, the government only seems to like parts of the doctrine. Somewhere along the way, the part of the 1947 plan that said corpus separatum could be put to a referendum of Jerusalem residents after ten years has fallen by the wayside.
The result of all this ancient history and failed diplomatic dogma is that the UK must maintain the fiction that Jerusalem is not the capital of Israel. That the Palestinian Authority has a comparably strong claim to a city which has never been part of any Palestinian state, since none has ever existed. That re-dividing the city is the way to deliver peace and uphold religious freedom, when Israeli control is the closest Jerusalem has come to underwriting religious co-existence. That splitting a capital city between recently hostile nations is a viable policy, or one with any successful precedent in the contemporary world. That by keeping up these pretenses the UK is hastening the arrival of a two-state solution rather than delaying it by pandering to and rewarding Palestinian rejectionism.