Willis has acquired former Willis Commercial Network founding broker CR King, following on from its recent acquisition of Opus Holdings.
The terms of the transaction for the Northampton-based CR King, which has revenues of £1.3m, was not disclosed.
A spokesman for Willis said it was not a specific strategy to acquire network members, but added: "If we have the opportunity to buy a broker that fits in with our UK plan then we do so."
CR King is the fourth UK acquisition since October 2004, following on from Opus Holdings, Coyle Hamilton, and CH Jeffries.
' Cardiff-based Culver Insurance Brokers is to leave Willis Commercial Network, with effect from 1 February. Culver chief executive John Powell said decision was reached by "mutual consent".