The President of Iceland Olafur Ragnar Grimsson joined the Southwark Cathedral congregation for Evensong on Sunday.
Choral Evensong was being sung on St Olave's Day with representatives of London's Nordic churches who are all hosting Olympic visitors.
The rector of St Katharine's Danish Church in Regent's Park, Else Hviid, read the first lesson in Danish and London's Swedish Dean Michael Persson read the New Testament lesson in Swedish.
Bishop of Visby Sven-Bernard Fast, known as bishop to the Church of Sweden abroad, preached on the first reading from Ecclesiasticus.
The prayers were led by Torbjorn Holt, rector of Rotherhithe's Norwegian church, and Teemu Halli, rector of Rotherhithe's Finnish church.
The service ended with the visiting Nordic Choir singing the Summer Hymn known as Sommarpsalm.
The Icelandic president was welcomed by Dean of Southwark Andrew Nunn.
Also present was Iceland's ambassador Benedikt Jonsson, Sweden's deputy head of mission Andreas von Beckerath and volunteers operating the traditional Swedish Olympic cafes, Cafe Svensson, at Swedish Churches in Marylebone and Rotherhithe.
Afterwards the Icelandic president viewed the Diamond Jubilee window, which has been designed and made by Icelandic artist Leifur Breidfjord, before attending a reception with visiting Olympic chaplains.
The service will be broadcast next Sunday on RUV, the Icelandic National Broadcasting Service.
• The Icelandic president was the second head of state to be at the cathedral during the weekend. On Saturday Swiss federal president Eveline Widmer-Schlump visited the Millennium Courtyard as part of her tour of the House of Switzerland.