The UK’s largest law firms are racing ahead in the adoption of artificial intelligence, according to new data from Thomson Reuters. Nearly 80 per cent of the top 20 firms have implemented third-party AI tools, while almost half are developing bespoke systems or partnering to build customised platforms. More than half are also providing AI training to their lawyers, and six firms have invested in AI start-ups or created in-house incubators to drive innovation.
Client engagement is keeping pace with internal investment. All of the top 20 firms have produced AI-focused reports or staged high-profile events to showcase their expertise, and all but one are actively promoting AI to clients. By contrast, among the next 20 firms only around 60 per cent advertise AI use and half have adopted third-party tools, underlining a widening gap between the elite and mid-tier. Across the top 40 firms, 78 per cent now promote their AI adoption, up sharply from 60 per cent a year ago.
The professionalisation of AI within firms is also advancing. The proportion of top practices with designated heads of AI has risen from 35 per cent to 45 per cent in the past year, while more than three-quarters have set up internal digital transformation teams. Smaller firms lag behind, with only a third creating dedicated AI departments. Yet sector-wide, just 24 per cent of law firms have formal AI strategies, leaving many still integrating AI without long-term planning.
Rising client expectations are a major driver. Thomson Reuters found adoption of AI among corporate legal departments and law firms has nearly doubled in a year, from 14 per cent to 26 per cent. Almost 60 per cent of corporate clients now look for panel firms that use AI, largely to gain efficiency and cut costs, while 8 per cent explicitly mandate generative AI in tender requirements.
“The UK’s very largest law firms are responding to pressure to adopt and integrate AI tools — but the next tier of law firms appears to be adapting more slowly,” said Raghu Ramanathan, president of legal professionals at Thomson Reuters. He warned this uneven pace is creating a perceived gap in expertise that mid-market firms must close to remain competitive.
The findings mark a pivotal moment for the UK legal sector. While the biggest firms are positioning themselves as leaders in AI-enabled legal services through investment, training and branding, the challenge remains to extend adoption more widely. Formalising strategies and fostering broader inclusion will be essential if the UK is to maintain its global leadership in AI-driven legal innovation.
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