The developer of London Bridge’s Shard tower is understood to have agreed a price of about £425m for the scheme with main contractor Mace

The sum is a saving of about £10m on the fixed-price bid that Mace submitted two months ago, but is still about £75m above the original estimate of £350m. An agreement would be the culmination of months of talks.

A source close to the project said: “They’ve basically reached agreement on the price. The signatures will be finalised within the next three weeks.”

The news emerged as investment company Qatari Diar announced it had agreed to provide finance for London Bridge Quarter, the joint venture body of Sellar Properties and four Qatari backers that is developing the 310m-high scheme. Qatari Diar will not take an equity stake, but will sit on the board of the organisation, which replaced Teighmore as developer after two original backers were bought out in January. Construction is expected to start next year.

The signatures will be finalised within the next three weeks source close to the project

Meanwhile, Mace announced that four of its senior board directors would be leaving the firm at the end of the year. Gary France, Steve Anderson, Mike Atkinson and Steve Booth will leave as part of the “succession planning” that followed its management buyout in 2001.

Stephen Pycroft, chief executive, said: “They have amassed more than 60 years’ service to Mace and it is time for the next generation to take up the challenge.”

• It is still unclear whether a restructuring within Transport for London (TfL), the Shard’s anchor tenant, could scupper its deal to take space in the building. A copy of a letter sent by TfL commissioner Peter Hendy to staff last week, seen by Building, says the organisation will conduct a “review” of all office locations in a bid to “reduce overhead costs” as it cuts staff.