Brit has formalised its bid for PRI. The move follows weeks of negotiations during which PRI indicated it would accept Brit's terms based on an informal offer.
The offer values PRI, a professional indemnity operation started last summer, at about £156m.
Brit would pay about 120p a share for PRI's entire stock.
Before the offer was made in late March, the shares were trading on AIM at around 115p.
