Thirty Nine Essex Street and 4-5 Gray's Inn Square are in "advanced discussions" about a possible combination that could see the two sets come together under one brand.

Should the tie-up go ahead, it would create one of the largest civil sets in London with around 140 members including more than 40 silks, and would be a rare example of consolidation at the bar. It is unclear whether the combination would include all barristers from both sets.

Recent weeks have seen a number of departures from 4-5 Gray's Inn, with two silks – Paul Brown QC and Philip Coppel QC – both leaving for Landmark Chambers alongside public law and planning barrister Lisa Busch.

Eleven King's Bench Walk (11KBW) has also picked up a group from the set, with commercial barrister David Bedenham and public law members Heather Emmerson, Charles Bourne and Andrew Sharland joining earlier this autumn.

Thirty Nine Essex Street is one of London's top commercial sets covering common, construction, costs, environmental and planning, energy, and regulatory and disciplinary law.

The chambers has offices in London, Manchester and Singapore, with the Asian base launching earlier this year.

Meanwhile, Gray's Inn specialises in public, planning and commercial law including a focus on civil liberties and human rights, defamation and privacy and education.

There has been increasing movement of barristers between sets over the last year, with 20 Essex Street taking on respected South Square silk Stephen Atherton QC and counsel Blair Leahy at the start of the year in a bid to expand into new areas of work.

Meanwhile, South Square silk Stuart Isaacs QC joined Berwin Leighton Paisner in November last year – marking a first step towards a full in-house advocacy offering for clients at the UK top 15 law firm.

News of the potential London combination comes after a trio of northern chambers: St Johns Buildings, Paradise Chambers and India Buildings Chambers, merged to create one of the UK's largest sets with more than 250 barristers at the start of last year.