The British government "expressed grave concerns" to the US government over the declassification and release of material related to the Trump-Russia investigation, according to the New York Times. President Trump ordered a wide swath of materials "immediately" declassified "without redaction" on Monday, only to change his mind later in the week by allowing the DOJ Inspector General to review the materials first.
The Times reports that the UK's concern was over material which "includes direct references to conversations between American law enforcement officials and Christopher Steele," the former MI6 agent who compiled the infamous "Steele Dossier." The UK's objection, according to former US and British officials, was over revealing Steele's identity in an official document, "regardless of whether he had been named in press reports."
We would note, however, that Steele's name was contained within the Nunes Memo - the House Intelligence Committee's majority opinion in the Trump-Russia case.
Steele also had extensive contacts with DOJ official Bruce Ohr and his wife Nellie, who - along with Steele - was paid by opposition research firm Fusion GPS in the anti-Trump campaign. Trump called for the declassification of FBI notes of interviews with Ohr, which would ostensibly reveal more about his relationship with Steele. Ohr was demoted twice within the Department of Justice for lying about his contacts with Fusion GPS.
Perhaps the Brits are also concerned since much of the espionage performed on the Trump campaign was conducted on UK soil throughout 2016. Recall that Trump aid George Papadopoulos was lured to London in March, 2016, where Maltese professor Joseph Mifsud fed him the rumor that Russia had dirt on Hillary Clinton. It was later at a London bar that Papadopoulos would drunkenly pass the rumor to Australian diplomat Alexander Downer (who Strzok flew to London to meet with).
Also recall that CIA/FBI "informant" (spy) Stefan Halper met with both Carter Page and Papadopoulos in London.
Halper, a veteran of four Republican administrations, reached out to Trump aide George Papadopoulos in September 2016 with an offer to fly to London to write an academic paper on energy exploration in the Mediterranean Sea.
Papadopoulos accepted a flight to London and a $3,000 honorarium. He claims that during a meeting in London, Halper asked him whether he knew anything about Russian hacking of Democrats’ emails.
Papadopoulos had other contacts on British soil that he now believes were part of a government-sanctioned surveillance operation. - Daily Caller
In total, Halper received over $1 million from the Obama Pentagon for "research," over $400,000 of which was granted before and during the 2016 election season.
In short, it's understandable that the UK would prefer to hide their involvement in the "witch hunt" of Donald Trump since much of the counterintelligence investigation was conducted on UK soil. And if the Brits had knowledge of the operation, it will bolster claims that they meddled in the 2016 US election by assisting what appears to have been a set-up from the start.
Steele's ham-handed dossier is a mere embarrassment, as virtually none of the claims asserted by the former MI6 agent have been proven true.
Steele, a former MI6 agent, is the author of the infamous and unverified anti-Trump dossier. He worked as a confidential human source for the FBI for years before the relationship was severed just before the election because of Steele’s unauthorized contacts with the press.
He shared results of his investigation into Trump’s links to Russia with the FBI beginning in early July 2016.
The FBI relied heavily on the unverified Steele dossier to fill out applications for four FISA warrants against Page. Page has denied the dossier’s claims, which include that he was the Trump campaign’s back channel to the Kremlin. - Daily Caller
That said, Steele hasn't worked for the British government since 2009, so for their excuse focusing on the former MI6 agent while ignoring the multitude of events which occurred on UK soil, is curious.