The absence of a permanent leader has worried investors looking for a recovery strategy from the company. Lonmin had one of the most stretched balance sheets in the sector even before it was hit in September by strikes at its flagship Marikana platinum mine, which became the backdrop for South Africa's worst violence since the end of apartheid. Roger Phillimore, Lonmin's chairman, said of Mr Farmer: "We will greatly miss Ian's ability, commitment and drive which he has devoted to the company over a career spanning more than 26 years. We wish him well with his ongoing treatment. Lonmin shares fell 3.7 to 2818p.