They will then move on to Chequers, the prime minister's country retreat in Buckinghamshire, for a working lunch and "bilateral talks on a range of global issues".
US President Donald Trump arrived Thursday in Britain, where he will find his own wall set up even as preparations for protests against his four-day visit are in full swing.
"We need to ensure there is a balance between protection and public safety and the public's right to peacefully protest".
The demonstrations are expected to attract large crowds.
In London, we speak with Sheila Menon, social justice activist and one of the organizers behind the Trump baby blimp. It will hover above Parliament Square later this week during the president's visit.
Although he will visit the USA ambassador's residence, he is largely avoiding central London, where the largest protests are expected Friday.
Such comments are likely to be seen as unwelcome by Mrs May, who has already faced significant political criticism for hosting Mr Trump.
But besides that, the United States president is set to avoid much of the mass protests as most of his official engagements have been planned outside London.
On Friday, as Melania Trump will accompany Philip May, UK PM Theresa May's husband, in visiting schoolchildren and veterans, Donald Trump will once again head outside the city to attend a military demonstration with his UK counterpart.
Referring to the separation of undocumented parents and children, they wrote: "It is with great sadness that we have followed reports of events in recent months which have seen families ripped apart and children placed in cages".
Considering Trump's comments yesterday referring to the United Kingdom as "in turmoil", it will remain to be seen whether he keeps his silence on the issue during his visit today. She pointed out there are many issues that legislators have urged her to raise with her American counterpart.
An inflatable, baby version of President Donald Trump could be appearing over his golf course in Scotland this weekend.
The prime minister will host a gala dinner and a meeting with Trump, giving them time to talk.
In fact, just the opposite, they say. The issue is 'Do they have freedom to protest, freedom to assemble and should they be allowed to do so?
But that could change.
Churchill spent three weeks at the White House, cementing his close ties with Roosevelt and forming the basis for future relations between the USA and Great Britain. "Britain is going to have to look right around the world for allies with which to do trade deals".
"Give us your tired and your oppressed and we'll divide you from your children", he said of Trump's policies.
Protests are expected against Trump, whose policies - including a travel ban on a number of predominantly Muslim countries, the detention of child migrants on the US-Mexico border and the imposition of tariffs on European Union steel and aluminium exports - have all been criticised by the UK. After a dinner for business leaders in Blenheim Palace, birthplace of Winston Churchill, he will spent the night in the ambassador's residence in north London.
It is not simply the protesters, who are expected to dog Trump throughout his visit, including his weekend in Scotland, but his fraught relationship with political leaders accustomed to harmonious exchanges with USA leaders, a tradition of unity that goes back at least to the vital World War II partnership of Franklin D. Roosevelt and Winston Churchill.