Freshfields has scooped the work on Clifford Chance's City desertion - the first time it has worked on a major deal for its rival.
The global firm, which spends nearly £40m each year on property costs, is abandoning its Aldersgate office in favour of one million square feet at Canary Wharf. It is understood the move will save Clifford Chance up to 15 per cent on its current rate of £40 per square foot.
The details of the 25-year lease are still confidential. But Canary Wharf is home to Clifford Chance's biggest clients. It is understood group legal counsel Michael Ashley-Brown views the deal as a "dream transaction".
Freshfields former property head and partner Geoff Le Pard is leading the transaction after first being approached in April.
Clifford Chance London managing partner Peter Charlton selected Freshfields because its booming City lettings practice represents a variety of Canary Wharf clients.
According to the Legal Insiders Guide to Commercial Property, the firm has developed an "excellent and heavyweight letting practice". Clients include Canary Wharf residents HSBC and Citibank.
Le Pard says he was both surprised and flattered to be asked to act on the move.
Clifford Chance is the first UK firm to quit the City for the East End development. It will retain a small City office although no lawyers will be based in it.
But Allen &Overy is understood to pay only £25 per square foot, while Norton Rose currently pays £24 per square foot, so Canary Wharf would have to offer an attractive package to lure the two top 10 firms.