British Land and Oxford Properties have announced that their 50:50 joint venture has signed a provisional agreement with a subsidiary of financial services group Aon for a 18,000 m2 pre-let at the 'Cheese Grater' tower development in London.

Aon has agreed to take the lower 10 floors of the offices (levels 4-13), and also has options to take up to a further 7,900 m2 of space on levels 14-18 of the 57,000 m2 Leadenhall Building.

At 224-metre, the 47-storey Leadenhall Building is set to become one of the tallest and most iconic buildings in the Square Mile, the heart of the City's insurance district. Construction of the tower started in January with practical completion scheduled for the mid-2014.