The final bill for London's Olympic stadium has risen again to almost £620m.
Olympic Park bosses have agreed to pay contractors an extra £36m to strengthen the roof.
The London 2012 venue is undergoing conversion work to allow it to be the new home of West Ham football club.
The work has turned out to be more complex and technically challenging than expected.
Contractors Balfour Beatty will now be paid £189.9m instead of £154m. The cost of building the showpiece arena already stands at £429m.