The shares, which were priced at 145p, shot to 162p in heavy early trading before settling down to close at 159p. There were trades as high as 165p, a full 20p above the issue price. "It's about where we thought it would be but I still think it will go to around 180p in the medium term," one analyst said.
Some of the debt holders in the original Isosceles parent company said they were unimpressed with the flotation which saw two price cuts and a last-ditch attempt by the advisers Kleinwort Benson to sell Somerfield, Britain's fifth biggest food retailer, to rival supermarket groups last week.
"We're not very happy and I think it was mishandled," one of the former debt holders said. "But having said that, the senior debt holders signed an agreement earlier this year agreeing to a minimum they would accept from the flotation. The proceeds cover that minimum."
Another debt holder said it was "displeased" with the flotation, but said it would not be filing any litigation against Kleinwort Benson, the German-owned investment bank, for selling the business too cheaply.
Another Isosceles debt holder said that any litigation might come from US investors such as the holders of junior debt and deep discount bonds who did not receive full repayment. However, the debt holder thought law suits were unlikely. "They all played the game and most of them have made some money trading the debt along the way."
Somerfield's chief executive, David Simons, was more positive: "I'm absolutely delighted that Somerfield is an independent company and we can get on with expanding the business."
He refused to comment on Kleinwort Benson's handling of the issue, which was the largest non-privatisation flotation of the year.
Somerfield blamed weak stock market conditions and a profits warning from Iceland, its rival food retailer, for cutting the offer price twice in the run-up to the flotation.