This would lift Anglo's holding in Lonrho to just under 30 per cent and provide the springboard for it to take charge of the group's platinum, gold and coal interests when the demerger of Lonrho's mining interests from its trading and hotels business takes place this summer. Anglo, which together with its asociates now owns 10 per cent of Lonrho, already had the option to buy Mr Bock's 18.4 per cent stake if he chose to sell.
Under the put and call deal agreed yesterday, Anglo has the right to buy Mr Bock's 143.5 million shares at 220p while he can force a sale at 180p.
The agreement is due to be exercised at the point of demerger. Anglo will buy Mr Bock's stake in the mining operations and tender its stake in the non-mining businesses in the subsequent flotation.
Mr Bock will use the proceeds from Anglo to acquire a 25 per cent stake in the quoted non-mining company which will own Lonrho's trading and hotel operations and will inherit the bulk of Lonrho's pounds 430m debt. Oliver Baring of SBC Warburg, which brokered the deal on behalf of Anglo, said: "I don't think Anglo is in bid mode but this puts them in a strong position where they can do all sorts of things."
A full takeover of Lonrho's mining operations could cause problems with competition authorities because it would increase Anglo's dominance of the platinum market, where it is the world's biggest producer.
But what interests Anglo more is Lonrho's 43 per cent shareholding in the Ghana-based gold producer Ashanti and its Duiker coal mining interests.
Announcing the agreement yesterday, Lonrho said it had decided that a closer partnership was necessary with Anglo to facilitate the separation of its mining and non-mining businesses.
Anglo meanwhile said it would co-operate with Lonrho to develop its gold and coal interests in Africa. A senior Anglo technical director has also been appointed to the Lonrho board.
"This allows people to get to know each other ... to go forward together in the demerger," Anglo spokesman Michael Spicer said.
The put and call arrangement will remain in place until 13 September, 1997. It values Mr Bock's stake at between pounds 260m and pounds 315m compared with a value at last night's 207.5p closing price of pounds 297m.