In the battle for London market share, the City M&A scene is one of the most competitive, with top UK practices coming under increasing pressure from uncompromising US counterparts.
While the deal value rankings tell one side of the story – with Latham & Watkins and Kirkland & Ellis taking the top two spots for 2025 – that data doesn’t give the full picture.
So for a different perspective on the City’s best deal teams, Legal Business took a deep dive into Legal 500 research to see which M&A departments were the highest rated by clients. (The following data is based on referee responses from Legal 500’s M&A: upper mid-market and premium deals research.)
Commercial knowledge
For commercial knowledge, Slaughter and May comes out top, ahead of Skadden and White & Case in second and third place.
The firm, which is known for advising more FTSE 100 companies than any other, had a role on the UK’s largest M&A deal of 2025, according to LSEG – advising a consortium of shareholders of Pension Insurance Corporation on its £5.7bn sale to Athora Holding.
Slaughters also led on the fourth largest UK M&A deal last year, guiding global instruments company Spectris through competing bids before its eventual £4.7bn acquisition by KKR.
Richard Smith (pictured), the co-head of Slaughters’ corporate and M&A group, sets out how the firm beds in client relationship. ‘We focus on our clients knowing us institutionally. They know a lot of partners across the firm, over our different practices, so they are being covered by the firm as a whole and that institutionalises the relationship,’ he explains.
‘There’s no internal politics about whose client is whose,’ Smith adds. ‘It’s a “one team” effort, fostered and enabled by our unique partnership culture and lockstep pay model.’
The firm placed seventh in LSEG’s 2025 rankings for UK M&A deal value, handling 50 deals worth a total value of $52.9bn.
Quality of partners
Slaughters also ranks highly for quality of partners, second only behind Macfarlanes and just ahead of Weil Gotshal & Manges.
Deal highlights for Macfarlanes during 2025 included advising Banco Sabadell on its £2.65bn sale of TSB to Santander, while the firm also acted for Stonehage Fleming and Stanhope Capital on their merger with US wealth advisory company Corient, which created a $430bn wealth management family office.
Macfarlanes M&A head Jessica Adam (pictured) said: ‘We place a deliberate emphasis on the very highest quality of advice, so it is encouraging to see that this is reflected in client feedback.’
She continued: ‘High value M&A demands clear judgement and practical insight, which requires a close understanding of our clients and their objectives. Our M&A partners are involved in every aspect of our clients’ most important transactions, bringing technically robust advice and real world deal experience to complex, cross-border and strategically significant deals.’
Partner availability and engagement
As well as strong client reviews for its commercial knowledge, White & Case has the highest score for the availability and engagement of M&A partners.
The US firm rose up the UK M&A deal value rankings last year, moving to sixth place from 20th in 2024, with roles on 77 deals including the fifth largest UK M&A deal of the year, according to LSEG – data centre development company Yondr Group’s $5.74bn acquisition by investor groups Digital Bridge and La Caisse.
Another international firm scoring highly in this category is Baker McKenzie, which handled a number of major mandates last year, such as advising Walgreens Boots Alliance on the carve-out and reorganisation aspects of its $23.7bn acquisition by Sycamore Partners. Global M&A head Jannan Crozier attributed the team’s strong showing to its emphasis on the ‘human connection’ in an industry where expertise is expected.
Overall client service
Another corporate team making a strong impression is Weil’s London M&A practice, led by City co-head David Avery-Gee (pictured), which shot up the LSEG M&A value rankings from 44th to 24th after handling 30 transactions valued at $16.5bn.
The firm worked on 2025’s second biggest UK M&A deal, advising insurer Convex Group on its $7bn (£5.2bn) sale to Onex and AIG, and it has already made headlines in 2026 with its role as lead adviser to Glencore on its potential $260bn merger with Rio Tinto, which could become the biggest M&A deal of all time.
While much smaller than many of its City peers, a clear pointer as to why the London team is punching above its weight lies in the assessment from clients.
The team scores in the top three for team quality, partner availability, and billing transparency – and, taking all metrics together to give an overall client service score, it comes out top above all of its peers.
All of the scores in this article are compiled from referee responses collected during Legal 500 research. Benchmark scoring for our other client service criteria is also available. Please contact [email protected] if you would like to know more.
