Technology group's listing plan

Promethean, which supplies interactive white boards and associated software to primary and secondary schools, is expected to be valued at up to 500m.

The firm, which is 25 per cent owned by private equity firm Apax Partners, was founded in 1996 by Tony Cann, whose family trust still owns 50 per cent.

It posted a 26 per cent rise in revenue to 205.1m in 2009, while underlying earnings rose 33 per cent, to 33.9m

The Blackburn-based company said a listing would enable it to pay off debt, and provide liquidity for shareholders, with Apax expected to exit.