Trump can never be a normal president
The `special relationship' is the unofficial term frequently used to described the close political, economic and historic ties which have always existed between the US and the UK.
Political leaders in the two countries invariably pride themselves on the friendships which remain in place, and their trans-Atlantic trips are a regular part of public life.
In this context, the confirmation that Donald Trump is to carry out a series of official engagements in London from June 3 to 5 could be presented as an unremarkable development.
However, Mr Trump is no ordinary president and the fact that his programme of events has been formally characterised as a state visit has caused considerable debate.
The invitation was instigated by the British government but sent, as protocol dictates, in the name of Queen Elizabeth, and it will be noted that it is only the third issued to a US president in the course of her 67-year reign.
While Mr Trump's status as the US head of state deserves to be respected, his record on a range of fronts as a public figure is disturbing.
The appallingly crude and offensive comments he made about women in 2005, and which emerged on tape in 2016 during what turned out to be his successful campaign for the White House, really should have ended his career.
When Republican Party supporters somehow gave him the benefit of the doubt, his aggressive attitude towards minority groups, his ludicrous plans for a wall along the Mexican border and his dismissive approach to international concerns over climate change have marked him down as perhaps the most contentious holder of his office in living memory.
He claimed that he was exonerated by the recent Muller investigation into his highly dubious links with Russia, but the firm indications that he attempted to obstruct justice during this process and separately his repeated and highly unusual refusal to release his tax returns all create the clear impression of a tainted presidency.
If Mr Trump arrives in Ireland later this year, as he has said is his intention, it can be expected that many political and civic leaders will take nothing to do with him.
Theresa May plainly holds a different view, but she will also be aware that an attempt to facilitate an address by the president at the Houses of Parliament will undoubtedly generate a strong reaction.
The real prospect of massive street protests, which would need to be peaceful and dignified at all times, means that any suggestion of a ceremonial procession through central London would present a security nightmare for the authorities.
It certainly appears that some of the standard elements of a state visit will be conspicuously absent, stressing to Mr Trump that, even within a special relationship, he can never be regarded as a normal president.