Bankside partner Simon Rothschild is advising Grant Thornton on PR strategy and handling press interest.
Founded by writer GK Chesterton in 1805, the upmarket estate agent celebrated its 200th anniversary at the National Gallery in January.
But the firm has become a victim of the property slowdown and last week axed 300 of its 700 staff from its commercial operation.
Last Friday, private equity firm CIC International announced it had agreed to buy Chesterton's 200-strong residential division. BNP Paribas real-estate subsidiary Atisreal is buying Chesterton's businesses in the City, Newcastle, Leeds, Southampton and Cardiff, which employ around 120 staff.
ICIS director Archie Berens is handling CIC. Clareville Communications, which works for Chesterton's residential portfolio, awaits a decision on its role.