Nearly 140 years since last PM appointed at Balmoral
BBC royal correspondent
It's been nearly 140 years since the last prime minister had to make the journey all the way up to the Scottish Highlands to be appointed.
That was in 1885. The PM then was Robert Gascoyne-Cecil. The monarch of course was Queen Victoria. It took several days for all the travelling.
Today it should be much quicker. The outgoing PM Boris Johnson will arrive here at around 11:30 having been driven from Aberdeen. He will tender his resignation to the Queen in the drawing room of Balmoral Castle.
Then shortly after midday, having been driven again the 45 miles from Aberdeen, the incoming PM Liz Truss will meet the Queen in the drawing room. She will be invited to form a new government, and from that point she will be PM.
The whole ceremony is known as the kissing of hands. In fact, there is no kissing, merely a handshake. And with that she will then return to London as PM to begin work.