Mayor of London Boris Johnson visited St Saviour's & St Olave's School on Wednesday morning to promote volunteering in the capital.
This year he stuck to safer territory: teaching a Latin class at an SE1 girls' school.
Mr Johnson arrived by bicycle at the Bartholomew Street school and was greeted by the headteacher Dr Irene Bishop as well as several prefects.
The Mayor was invited to sign the school visitors' book and leave an inspirational message in Latin. After some head-scratching he chose a text from Virgil.
Mr Johnson joined a class of pupils who have been learning Latin and Ancient History after school since September. He sat in on a session about chariot racing before taking over to teach some Latin phrases.
He declared himself very impressed by the pupils' knowledge of Latin and urged them to continue to study the language which he described as "a great tool for understanding languages across the world".
"Look at me: I did almost nothing but Latin and Greek for 25 years and now I'm in charge of every bus in London," said the Mayor.
Dr Irene Bishop said: "We were delighted to welcome Boris to our school and appreciated his contribution to our class. We couldn't provide enrichment opportunities such as Latin without the hard work of our teachers and our partnerships.
"For Latin studies we have benefited from volunteer teachers from Dulwich College and James Allen's Girls' School (as part of our independent/state school partnership) and now from the A level students from Westminster School. MAGNIFICUS! EUGE!"
The Mayor has given all Greater London Authority staff three days a year leave for volunteering activities. His advisers and directors will be involved in a variety of activities during Volunteers' Week and on an ongoing basis. Events include restoration work on HMS Belfast and an environmental task force for Capital Clean-up.