Boris Johnson will not be attending the Mayor of London's Carol Service this year because he is visiting the climate change summit in Copenhagen.
The theme of the event at Southwark Cathedral on Tuesday evening will be 'Service to Londoners', in recognition of the work of the police, the fire service, ambulance and nursing staff, as well as the armed forces – all of whom will be represented at the service.
The Deputy Mayor of London, Richard Barnes AM, will represent Mr Johnson on Tuesday evening.
The London Gay Men's Chorus will be among those taking part in the service. All are welcome to attend the event which begins at 7pm; doors open at 6pm.
The Mayor's Christmas Carol Service was held for the first time in 2008 at the instigation of the incoming mayor, Boris Johnson.
Mr Johnson's absence on Tuesday means that he will be unable to take up the Dean of Southwark's invitation to read from the Bible in Greek.
"[The Mayor] and I engaged in a delightful sparring match concerning biblical translations," wrote the Very Revd Colin Slee in his annual report on cathedral activities.
"Being a good classicist, he flourished a copy of the New Testament 'in the original' (which so many people believe to be the Authorised Version!) and so I have invited him to read The last Gospel (John 1: 1-14) in Greek this year, with the English text printed in the service booklet."
At last year's carol service there was momentary confusion amongst the congregation when the Mayor began to read from the traditional language King James version ("the life was the light of men") rather than the inclusive New Revised Standard Version text ("the life was the light of all people") printed in the order of service.
Although Mr Johnson will miss the service on Tuesday evening, he will be back in the capital on Wednesday morning to answer questions from the London Assembly at City Hall.