Guyerzeller is three-quarters owned by Samuel Montagu, the merchant banking arm of Midland, and the British bank’s deputy chairman Sir Michael Palliser is a director of the Zurich operation links of london sale. But Midland refuses to say who has the minority share in Guyerzeller other than it belongs to a mining company. Guyerzeller’s general manager Mr Hugo Bohny says enigmatically: ‘We don’t talk about our shareholders.’

 But documents obtained in the Netherlands show the bulk of the remainder of Guyerzeller is in fact owned by a Dutch holding company links of london, Matron BV, whose parent is Central Holdings – the cornerstone of the Oppenheimer network in Europe. This explains why Mr Grey Fletcher and Mr Edward Dawe, both directors of De Beers, sit alongside Sir Michael on the Guyerzeller board.

 The ownership link is reinforced by multiple cross-directorships in Oppenheimer companies – usually offshoots of De Beers – held by key officials in Guyerzeller and Vadep valentine’s bracelet .

 Among those officials, Mr Andina stands out. In his late 50s, Andina has worked for Guyerzeller for 27 years, since well before it became a Midland company. He joined the bank’s board four years ago and is now an executive director.

 Mr Andina is an officer of about nine Swiss De Beers companies. Last year he was appointed a member of the Conseil d’Administration of Central Holdings valentines Day rings . Some Guyerzeller colleagues have similar links with Swiss De Beers companies.