A major concert in Trafalgar Square is among a programme of free events that are to be held in London in April to celebrate St George's Day, under new plans announced by mayor Boris Johnson.

In addition to flying the English flag outside City Hall on 23 April, Johnson will take part in St George's Day celebrations at Leadenhall Market in the City of London, while the concert will take place on Saturday 25 April. The five-and-a-half hour concert will include a number of folk artists inspired by the English tradition, including the Mercury Music Prize-nominated acts Seth Lakeman and Eliza Carthy, as well as Bishi and Kathryn Tickell.

An event is also planned for Sunday 19 April at Shakespeare's Globe Theatre in Southwark to mark the 400th anniversary of the publication of the bard's sonnets, which will include sonneteers, interactive games and activities. Johnson said: "St George's Day has been ignored in London for far too long, but I'm truly pleased to announce some fantastic events to mark this occasion. We have much to be proud of in this great country, England has given so much to the world politically, socially and artistically.

"St George's Day is a time to celebrate the very best of everything English and the Cross of St George will proudly fly outside City Hall on 23 April. I look forward to hopping on a Routemaster and visiting Leadenhall Market for traditional English festivities."