In a highly unusual move, Lonrho invoked the disclosure provisions of the Companies Act to force the information out of Mr Bock's private business interests. According to Tiny Rowland, Lonrho's founder, the disclosures call into question Mr Bock's financial standing and independence.
Mr Bock still owes the Frankfurt-based Bfg bank nearly all the pounds 100m he borrowed to help buy his Lonrho stake. However, he insists his only obligation is to repay the loan and interest, and maintains that at the outset the German bank refused to accept Lonrho shares as security.
The revelations, made on BBC2's The Money Programme tonight, dispel some of the mystery that has surrounded Mr Bock's financial affairs and heighten mounting tension between Lonrho's chief executives. The company is shortly due to report lower-than-expected pre-tax profits for 1992 of about pounds 80m.
Laerstate, the Dutch company through which Mr Bock holds the Lonrho shares, wrote to Lonrho at the end of October with full details of the financial arrangements made to buy the shares.
Lonrho had invoked Section 212 of the 1985 Companies Act to obtain information from a number of banks. Mr Bock had previously refused to give full details of how his Lonrho shares were financed.
The letter from Laerstate discloses that the London branch of Bfg bank 'is interested as a chargee' in 143,487,260 Lonrho shares, Mr Bock's entire holding at present.
Mr Bock also has an option to buy a further 45 million shares in 1995 which, the letter confirms, Credit Suisse of Zurich is 'interested in, as escrow agent'.
According to Mr Bock, he took out ''a private loan' with Bfg bank enabling Laerstate to buy the Lonrho shares, costing a total of pounds 135m. Mr Bock insists that the balance - about pounds 35m - was financed out of his own resources and paid to Lonrho in instalments.
'The amount that I still owe to the bank is less than pounds 100m,' he said. This is secured against the Lonrho shares, though to begin with he had to put up shares in his German property company, Advanta, instead.
'Initially the bank didn't want to have Lonrho's shares as security. Maybe they didn't trust enough Lonrho's shares at the time. Later on, about six months later, they felt more comfortable with Lonrho's shares, so I could replace the security I gave at the beginning and give them the normal shares I bought as security.'
However Mr Rowland, who now owns 6.4 per cent of Lonrho, said: 'It's going to be very difficult to exclude me from the running of Lonrho, because I'm still perhaps the largest shareholder in terms of shares unpledged - 50 million shares that are not pledged to the banks and that are worth pounds 60m, pounds 70m or pounds 80m.
'I'm totally independent. Other people may have pledged their shares to the banks and need to satisfy the banks that their investment is sound and that the bank has adequate security,' he added.
Mr Rowland declined to go into the details of Mr Bock's personal financial position, although it was outlined in the Laerstate letter and sent to Lonrho's head office more than two months ago.
Mr Bock vehemently denies he is beholden to the bank. 'If I fulfil my obligations, which consist of paying interest at a later stage and paying back the loan, that's all I have to do. There aren't any more links and no obligations at all,' he said, adding that there was no time limit on the loan.
Friction between the two men has been increasing over recent months. Mr Bock has been attempting to introduce a number of changes to bring Lonrho more into line with practices at other big companies.
His aim is to make Lonrho a more attractive investment to institutional shareholders. Mr Bock wants the company to adopt the kind of best practices in corporate governance recommended by the Cadbury committee.
'In my opinion a company of this size has to act like many other public companies, which means everyone on the board has to be involved in the business, has to be involved in decisions,' he said.
'That means we have to follow the necessary requirements of Cadbury and other regulatory steps many other companies have to undertake.'
Changes have included the appointment of non-executive directors, new accounting procedures and, most recently, proposals to change Lonrho's articles of association. This could have the effect of obliging older board directors associated with Mr Rowland to retire.
However Mr Rowland, who is 76, would not be affected by this. Mr Rowland said he had nothing at all against some of the changes introduced by Mr Bock. But he added: 'If there are audit committees, or if there are cash committees and so forth, they have nothing to do with me.'
Lonrho is expected to announce full-year results later this month.
Tessa Curtis is a reporter for BBC TV's 'The Money Programme'.