The Bishop of London is urging unity across Christian denominations as he retires at a time of "great promise and great peril".

Rt Rev Richard Chartres will step down from the number three role in the Church of England later this month and gave his valedictory sermon to a packed St Paul's Cathedral on Thursday evening.

The 69-year-old joked a bishop's fixed retirement age of 70 was "like a divine sacking" as he departs after more than 20 years as Bishop of London.

He described his diocese as being "at the world's crossroads" and called it to be "a Church which aims to bring people together rather than prise them apart".

In a veiled attack on US President Donald Trump, Chartres criticised those who react "to change by insisting on ever narrower definitions of their identity" and called on the Church to stand firm.

"We belong to a transforming community reaching after a wider and wider sense of 'us'," he said. "We have the freedom to act and not be immobilised by the pressure of the passing moment."

Once tipped for the top spot of Archbishop of Canterbury, Chartres comes from the Church's Anglo-Catholic tradition and has refused to ordain women, which has endeared him to his diverse and disparate diocese's conservative wing. 

A close friend to the Royal Family, Chartres was a witness to Princess Diana's will and gave her memorial sermon in 2007. He confirmed Prince William and preached the sermon at his wedding to Kate Middleton on 29 April 2011.

Chartres is responsible for the CofE's relationship with the Orthodox Church and was the Anglican representative at the enthronement of Patriach Kirill I as head of the Russian Orthodox Church in Moscow.

He used his final sermon at St Paul's Cathedral to urge greater cooperation between all Christian Churches and said by "living with diversity and difference, we open ourselves up to grow and be transformed".

He said: "We should seek partnerships in the gospel at whatever level we are working.

"We should seek alliances in the wider household of faith in building a servant community whose attractiveness pagans will not be able to deny."

He told the congregation of several hundred: "The problem is that our project of growth without limit with no end in view beyond the accumulation of more and more things, this project is unsustainable."

He added: "What the Church has to offer is not an ideology or a mere critique but a community in which the Spirit of Jesus Christ dwells. In a market place of strident salesmen of warring ideologies we seek not to add to the din but to build relationships that endure and give meaning to life."