The deal was rushed through yesterday after Crown Communications, LBC's parent, was placed in receivership.
Mr Porter confirmed that Lady Porter would probably join the board of LBC in the near future. The company had given assurances to the Radio Authority, the industry's regulatory body, that it would seek to appoint a 'left-leaning director' to ensure political balance if she joined the board.
Chelverton had been in negotiation with Crown's management since last November about taking an interest in the radio station. It will inject pounds 7m into the business to keep it running until the franchise, due to expire in October 1994, is re-advertised later this year.
Talks were accelerated after Crown's bankers, ANZ and Bank of Scotland, withdrew support for the company on Wednesday night, prompting the directors to call in administrative receivers from Arthur Andersen.
Crown, which lost pounds 6.8m in the year to September 1991 and a further pounds 5.6m by March last year, had been in trouble since advertising revenues started to decline in 1990. It failed to increase its audience share when it split its service between the AM and FM wavebands, and problems increased after it took a stake in RFM, a loss-making network of French local radio stations.
The banks lost patience after the CSA, the French regulatory body, blocked a sale by Crown of its holding in RFM. The regulator is understood to have accused Crown of raising its holding in RFM above the legal limit.
Crown said yesterday that it was amazed by the CSA's decision and emphatically rejected the charge. The receivers will meet the CSA soon to ascertain whether the sale, to a French consortium, can now go ahead.