Fortis Bank has agreed terms on the top floors of St Martins Property Group’s 150 Cheapside scheme.
If the deal is completed then rival bidder, US law firm Orrick Herrington & Sutcliffe will have to look elsewhere, Property Week has reported.
Fortis are hoping to secure 60,000 sq ft of the development, which is due for completion later this year.
The deal will provide positive news for the City’s commercial property market, which has seen few large transactions of late.
Orrick had planned to occupy between 70,000 sq ft and 100,000 sq ft of the development and sub-let to Investec, who Property Week has reported is interested in renting space on its own.
The last major rental deal in the City was back in May, when Standard Bank took more than 100,000 sq ft of space at 20 Gresham Street.