BrightReasons, which owns the Pizzaland chain, is to pay pounds 20.25m for Rank's Pizza Piazza and Prima Pasta businesses.
The group was founded in 1991 by Mr Guthrie, former chairman and chief executive of Mecca Leisure. He left Mecca following Rank's acquisition of the company.
Mr Guthrie said the deal would add about pounds 20m a year to BrightReasons' current turnover of pounds 150m, and would bring its total number of restaurants to 165.
But he would not be drawn on speculation that the group would seek a stock market listing.
'Certainly the business is capable of being floated, but we don't need to float for funds, so I'm in no rush,' he said.
'Our 165 restaurants now make us a pretty big player in the field and we now take the opportunity for more organic growth at the margin, by adding on units.'
A spokeman for Rank said the disposal marked another stage in the group's strategy of divesting what it regards as non-core businesses. Rank is keen to reduce its pounds 1bn debt burden.
It sold its chain of 11 motorway service stations to Pavillion Services, another company controlled by Mr Guthrie, at the end of 1991.
Rank shares closed 2p higher at 695p.
Prima Pasta, which has 16 outlets, was part of Mecca before the leisure group was taken over by Rank in 1990.
BrightReasons already has another pasta chain, Bella Pasta, and Mr Guthrie said the acquisition gave the company critical mass in a growth market. 'We created Prima Pasta at Mecca, so I know the business and was in a better position than most to make a judgement on its value,' Mr Guthrie said.
He added that the acquisition of the Pizza Piazza business gave the group a better spread in the pizza restaurant market, where it already has a presence through Pizzaland. 'Pizza Piazza operates at the higher end of the market, much like PizzaExpress.'
The deal is funded by Mercury Development Capital, which has financed the group since its birth. Mercury has brought in Montagu Private Equity as another investor. Debt has been arranged by Samuel Montagu, which is providing the facilities in conjunction with Bank of Scotland.
BrightReasons is paying pounds 19m cash immediately to Rank, with a deferred consideration of pounds 1.25m payable in October 1994.Reuse content