Brit's bid to buy up professional indemnity insurer PRI has become unconditional.
The offer now remains open for acceptance until further notice.
By last Thursday, Brit's offer had been accepted by shareholders representing 96.1% of PRI's total stock.
Brit already owned a small shareholding before it made the offer.
This means Brit owns or has acceptances covering 96.7% of PRI's stock.
Brit chairman Clive Coates said: "This is a tremendous leap forward for Brit.
"We believe the combined businesses of Brit and PRI provide an excellent opportunity to service the UK and other insurance markets."
Brit chief executive Neil Eckert said: "This transaction further establishes Brit as a market leader in the UK small to medium commercial insurance sector."