LONDON Britons love a dollop of nostalgia. And theres nothing more likely to make its politicians more wistful than the long shadow of wartime hero Sir Winston Churchill.

In 1946, it was Churchill who gave a speech in Fulton, Missouri, to declare that the United States and Great Britain had a special relationship that was essential for keeping the global peace.

Some 73 years later, Donald Trump has begun his UK State Visit in customary style, launching a Twitter tirade at London Mayor Sadiq Khan just minutes before Air Force One touched down.

Hed earlier praised Theresa Mays political rival Boris Johnson in a pre-trip interview , in which he also called the Duchess of Sussex nasty and claimed outgoing Prime Minister May had bungled Brexit.

The rocky opening was enough for the Washington Post Editorial Board on Monday to describe the visit as a low moment for the special relationship , that will serve to put on display the widening cracks that Trump has introduced into one of Americas closest alliances.

Yet, as Trump holds meetings with senior UK politicians on Tuesday, many on the British side of the Atlantic are already wondering whether it is now time for a conscious uncoupling.

Just at the time when Brexit is set to make the UK more dependent on the United States, and less close to the European Union, Trumps America First approach to trade and diplomacy has little room for sentiment, even for an old ally.

Normally, when a country hosts the leader of a friendly nation, big joint investment deals are arranged in advance, PR gifts ready to be unwrapped by the politicians.

This time, there are no plans for a major announcement of US and UK companies delivering fresh contracts or jobs. Business chiefs will gather in Downing Street, but the twin threats of a global trade war with China and of a no-deal Brexit make many in commerce nervous.

As Trump refuses to listen to London about the urgency of tackling climate change, or sticking with the Iran nuclear proliferation deal, this always unbalanced partnership feels more than ever like an unrequited love affair.

Its true that in some areas, the president has been influenced by May on issues, such as sending home Russian spies after the poisoning incident that killed two British nationals.

And hes been more than grateful for British support for his constant plea for NATO countries to spend more on their own defence budgets, rather than relying on Americas troops and cash.