He made a name for himself by fighting hard to keep National & Provincial Building Society independent when it sought a partner over a year ago, but N&P was eventually bought by Abbey National. Mr Lyons stayed on as managing director of Abbey's insurance division and played a key role in merging the two institutions.
His new role will again be high profile, as NPI is being stalked by Australian Mutual Provident. City sources suggest a selling price of around pounds 2bn if AMP is successful.
Mr Lyons said yesterday he intended to champion NPI's status as an independent, mutual company: "I've come into this business to build it, not sell it.
"I'm a passionate believer in mutuality. It's the best deal for the customer since there is no sharing of the value created in the company with a third party - shareholders."
Mr Lyons will succeed Kevin McBrien as chief executive of NPI. The company is based in Tonbridge in Kent and has around pounds 10bn under management, with 390,000 policyholders. It sells its products through independent financial advisers.
NPI said Mr McBrien would retire from the board at the beginning of July and Mr Lyons would take up the post of chief executive in June.
Mr Lyons said: "I enjoyed working with Peter Birch [chief executive of Abbey National]. It was a great period. I always said to Peter that I wanted to be chief executive of my own business at some point, but not before N&P was fully integrated with Abbey."
He said that long-term savings were the fastest-growing area of financial services because of demographic reasons. "Because of our relative small size [at NPI] we can run rings around the competition."
Mr Lyons denied that he was doing a U-turn on mutuality, having caved in to Abbey's bid for N&P. "N&P's branches and advisers needed investment, but the size of the business meant we couldn't sustain that investment. That is why we decided we needed a partner, which meant we needed to demutualise.
"NPI is completely different. It is a tightly focused business which doesn't need to demutualise."
Despite his enthusiasm for mutuality, Mr Lyons denies that the current wave of conversions to plc status among building societies and insurers has gone too far.
"If all the societies and insurance companies had converted then that wouldn't have left future generations with a lot of choice over financial services. What these conversions have done is to act as a very healthy catalyst to force the remaining mutuals to be more competitive."
Halifax, Woolwich and Alliance & Leicester building societies are converting this year. Mr Lyons said that while he did not know which direction they would take, their managements had been acting for years as if they had already converted.