(Reuters) — Retail tycoon Philip Green admitted to British lawmakers on Wednesday he had erred in selling BHS Ltd. to a former bankrupt and promised to help fix a gaping hole in the pension plan of the collapsed department store chain he owned for 15 years.

The loss-making BHS fell into administration in April, little more than a year after Green sold it to Dominic Chappell's Retail Acquisitions Ltd. for a nominal sum, resulting in the likely loss of 11,000 jobs as it is wound down. Mr. Chappell was a serial bankrupt with no retail experience.

BHS' demise left its pension fund with a deficit of £571 million ($809 million), while Topshop-owner Mr. Green's reputation as a leading British businessman was tarnished.

In a six-hour session in front of parliament's Business and Work and Pensions committees, Mr. Green was at times contrite, at times exasperated, and at one point came close to walking out.

He apologized for BHS' "sad ending" and his role in it.

"It was an honest mistake and unfortunately we sold it to the wrong guy," said the 64-year-old billionaire. "I'm a big boy, I'm going to take a punch on the chin."

He said he was working on a plan to plug the pension deficit, calling the situation "resolvable, sortable."

But there were also flashes of annoyance as Mr. Green was probed more deeply. Exchanges were often heated, and he frequently interrupted lawmakers and complained about their lines of questioning.

Mr. Green said he had trusted Mr. Chappell as a buyer because he had been approved by Mr. Green's adviser The Goldman Sachs Group Inc. and was being represented by law firm Olswang L.L.P. and financial adviser Grant Thornton L.L.P., names he called "reputable, well-regarded."

He said Mr. Chappell's status as a former bankrupt was not a reason not to do business with him. "Walt Disney was bankrupt, HJ Heinz was bankrupt, they did OK," he said.

Last week, Mr. Chappell told lawmakers he accepted partial responsibility for BHS' collapse, but said Mr. Green and the retailer's management should share the blame.

Pension regulator

Mr. Green was critical of the pension regulator for failing to engage with BHS as its deficit increased and said the retailer's pension trustees were also responsible.

He said he had not received one phone call or email from Lesley Titcomb, the pension regulator's CEO, calling for a meeting in the three years since 2013 when it started examining BHS.

Mr. Green also denied he scuppered a last-ditch rescue of BHS by Sports Direct International P.L.C. owner Mike Ashley and said he considered buying back the business.

He did not provide details on the plan he is working on with Deloitte to plug the pension deficit — a figure based on how much it would cost to address the shortfall between assets and future liabilities with either insurance or a buyout — as he sought to reassure BHS' 20,000 pension-holders.

"We will sort it, we will find a solution," he said.

He told lawmakers the plan would offer BHS pensioners a "better outcome" than compensation available from the Pension Protection Fund, the levy-funded U.K. lifeboat scheme that helps finance pensions after company insolvencies.

The deficit compares with the £423 million of dividends Mr. Green paid out during his ownership of BHS from 2000-2015, mainly to his family.

Stop staring

Some politicians have called for the tycoon to be stripped of his knighthood if he does not make good the deficit.

Feeling the heat from lawmakers, Mr. Green asked Richard Fuller from the ruling Conservative party not to stare at him and complained a whispering committee clerk was putting him off. Filling a plastic cup of water, Mr. Green spilt it over his table.

Iain Wright, the opposition Labor party lawmaker who chairs the business committee, said Mr. Green had a "dominant personality" and that could have had implications for BHS' culture.

"You seem extraordinarily thin-skinned to quite courteous questions, as if you don't want to be challenged in any way shape or form," Mr. Wright said. Mr. Green refused to respond.

The marathon session was not, however, without humor. At one point Mr. Green's phone went off, prompting Wright to say: "It's the regulator."