It's like something from a John Le Carré novel.

The Patriarch of the Russian Orthodox Church (ROC) visits London. He consecrates a new cathedral and meets the Archbishop of Canterbury and the Queen.

The visit is to celebrate 300 years of Orthodoxy in Britain. There are some nice historical touches – the Queen was represented at the consecration of the cathedral by her cousin Prince Michael of Kent, who has family ties with the Romanovs and bears an uncanny resemblance to Tsar Nicholas II.

Should he have been welcomed so warmly by the establishment? Some think not, given the ROC's close ties to President Putin's regime. Labour MP John Woodcock told the Daily Mail that it was "very troubling" for Kirill to be welcomed to Buckingham Palace at a time when Russia is supporting a "murderous Syrian regime". Another MP, Alison McGovern, said it was an "inappropriate PR opportunity". Ukraine's ambassador to the UK said the visit risked legitimising Russia's aggression in her own country.

Behind the diplomatic front, however, are intrigues and power plays, both political and ecclesiastical.

This was an iceberg visit, in which most of the significant issues – both ecclesiastical and political – are under water. For instance, a statement from Justin Welby's office rather implied everything in the Lambeth Palace garden was rosy. The ROC's take was a little different: its representative Alexander Volkov said Kirill had told Welby the ROC was "seriously concerned with liberalisation of the teaching of the Anglican Church in questions of church rules – consecration of women to priests and bishops, and in morals and family issues". In Lambeth's version, this becomes: "Conversation also touched upon the concerns and challenges that their two churches face in the present time in their different contexts." However much the ROC will play along with the necessary ecclesiastical diplomacy, its opposition to homosexuality and to women priests is adamantine – hence its unlikely alliance with the Billy Graham Evangelistic Association, with which it had planned a summit in Moscow on religious liberty, now postponed.

The consecration – or re-consecration – of the cathedral, too, is significant. Great Britain and Ireland form the Diocese of Sourozh (Moscow Patriarchate). The diocese was established in 1962, but after the fall of communism there was a large influx of Russians into the UK who were unhappy with the Orthodoxy they found here, which they thought wasn't Russian enough.

An extraordinarily bitter battle for control of the Church followed, in which a leading role was played by Metropolitan Hilarion Alfeyev, now the ROC's foreign secretary. Hilarion was appointed by the Moscow Patriarchate to be the assistant bishop of the Sourozh diocese. He was being groomed by the ROC to succeed Metropolitan Anthony and to "Russify" UK Orthodoxy. Anthony issued an open letter in which he criticised Hilarion's appointment and said he didn't know how to be a bishop; Moscow backed down and brought him into its department of external affairs, where he has remained.

The affairs of the ROC in the UK during this period – 2002 onward – are extremely complicated and unedifying, with continuing battles between those who favoured a more native style of Orthodoxy and those who wanted it to be more Russian. The Cathedral itself became a focus of the conflict. In 2006 many of the clergy and laity, headed by Bishop Basil Osborne, decided to leave the ROC and transfer to the Ecumenical Patriarchate of Constantinople; in 2007 the Cathedrals parish council decided to take the building with them. It took a High Court action by the Moscow Patriarchate to retain it for the ROC.

So the consecration of the church as a cathedral by Patriarch Kirill – with Bishop Hilarion in attendance – represents a comprehensive victory by the ROC and an assertion of Russian power over the decadent UK Orthodox faction. Bishop Hilarion's feelings at the service can probably be guessed at.

Another victory is being celebrated today in Paris, with the consecration of another cathedral. Near the Eiffel Tower and topped by five massive golden domes, the cathedral is to serve as a "spiritual centre" and school as well as a place of worship. It is close to government agencies including the foreign ministry, and intelligence services are worried that it will serve as a base for spying. Again, it is in part a political statement: a split in the ROC after the Russian Revolution saw many Russian congregations join the Ecumenical Patriarchate, and they have refused to rejoin the Moscow Patriarchate. Their cathedral, St Alexander Nevsky, will be outshone by the new one. Russian Orthodoxy, vastly wealthy and assertive, is making its presence felt throughout Europe.

The consecration of that cathedral, however, has had to take place without one of its principal guests of honour – Vladimir Putin. He was originally scheduled to attend, but pulled out over France's fierce criticism of his Syria policy – President Hollande had said he would raise the issue with him.

But back to London. A little-noticed remark in Kirill's sermon at the cathedral indicates another reason for his presence. He said: "When at the beginning of the eighteenth century diplomatic relations between the two countries [Russia and Britain] were broken off, the rector of our church here in London carried out a state and diplomatic mission. And this would happen every time when relations between the two countries became difficult."

In saying this, Kirill – himself a former KGB agent – was pointing, perhaps a little undiplomatically, to the role the Church could play in acting as a back channel for diplomatic conversations. Governments might be unable to speak to each other civilly – Putin in France, for instance – but there are ways of talking even so.

And in an unreported note on the ROC's website yesterday, we discover that Metropolitan Hilarion – yes, the same – met Baroness Anelay, minister of state for the Commonwealth and the UN at the Foreign and Commonwealth Office. They were joined by Laurie Bristow, Britain's ambassador to Russia, and among other things they discussed Syria and the Middle East. Evidently Hilarion tried to defend Russia's ally, President Assad; by her own account, Anelay told him off in no uncertain terms. 

It really is like a Le Carré novel.