MILLIONS of savers in Britain are set to enjoy hefty cash windfalls as the Halifax Building Society abandons 144 years of mutuality and joins the stock exchange today.

Around 7.6 million Halifax members will become shareholders in the flotation.

Those who have decided to sell their shares immediately could receive windfalls of up to £2,300 sterling on average.

Halifax's brokers Merrill Lynch and Cazenove auctioned 23 per cent of its flotation shares on Friday to institutional investors.

Analysts said there would have been aggressive bidding at this auction from institutions which missed out on the strong early performance of another building society, the Alliance & Leicester, when it floated last month.

The result of the auction of almost 570 million shares will be announced this morning.

Halifax has guaranteed shareholders selling their entitlement at auction that they will receive at least 415 pence per share.

But analysts predict the shares will be worth considerably more than this.

They believe the auction price could be 650720 pence per share, valuing the company at £18 billion and making it one of Britain's 10 largest.

Until now Halifax, like Britain's other building societies, has been owned by its savers and borrowers - known as its members.

Last February, they voted in favour of a proposal for the society to convert to a public limited company and float on the stock exchange.

Analysts say Halifax will be a leader in the financial services industry, with a profitable existing franchise and extensive capital reserves - estimated at more than £3 billion.

"The flexibility Halifax's listing provides it with, together with its dominant shares in both the mortgage and liquid savings market, suggest it is likely to be a significant competitive threat," BZW analyst Mr Timothy Sykes said in a recent report.

This echoed an earlier report by Goldman Sachs which said Halifax would "ultimately be one of the winners in the current battle for supremacy in the UK financial services market".