The UK Second 50 – the country's law firms ranked 51-100 by revenue – generated combined turnover of almost £2bn last year, as competition for places continues to drive growth outside of the UK top 50.

For the first time ever, Legal Week has this year extended its UK revenue rankings to cover the largest 100 law firms, with the Second 50 stretching from Brown Jacobson, with revenue of £73m in 51st place, down to Fox Williams, the UK's 100th largest law firm with revenue of £22m.

Total revenue for the group stands at £1.98bn, up 8% from £1.83bn last year, with 90% of the group posting increased turnover on 2016-17.

The fastest-growing firms among the 50 included JMW Solicitors, which boosted its top line by 30% from £25m to £32.5m during 2017-18, while 15 other firms posted double-digit growth during the year, including four above 20% – Harbottle & Lewis (26.3%), Gordon Dadds (25.3%), Keystone Law (23.9%) and Wiggin (20.4%).

The group's overall revenue growth lags slightly behind that of the UK Top 50, which saw total turnover rise 12% in 2017-18 to a new high of £22.5bn.

Merger deals were a significant driver of growth in the UK Top 50 last year, and four firms in the Second 50 have recently confirmed tie-ups that will shake up the established order next year.

Ashfords, 70th in this year's rankings, has agreed to merge with Reading's Boyes Turner, creating a £60m firm on the fringes of the UK Top 50, while 81st-place Bircham Dyson Bell recently combined with Pitmans to create a £50m firm under the banner of BDB Pitmans.

Kent-based firm Cripps is also set to rise from 83rd in the rankings after its £45m merger with Pemberton Greenish, while the biggest deal will see Gordon Dadds enter the UK Top 50 next year, with its reverse takeover of Ince & Co set to create a £110m-plus firm known as Ince Gordon Dadds.

Average profit per equity partner (PEP) among the Second 50 stands at £424,000 for 2017-18, marginally down on last year's equivalent figure of £427,000, and significantly lower than the Top 50's average PEP of £719,000.

However, the Second 50 does contain a handful of highly profitable firms, including Stewarts, with PEP of £1.4m, and Dickson Minto, which does not disclose its profitability but is understood to have PEP upwards of £1.2m.

Firms enjoying significant PEP growth during 2017-18 included Lewis Silkin (up 54% to £325,000), Capsticks (up 47% to £419,000) and Michelmores (up 45% to £301,000).

• Click here for the full table of results from the Second 50, and click here for coverage of the UK Top 50