David and Simon Reuben are reported to have built up small stakes in Whitbread and Rank, fuelling speculation of a break-up of the companies. The brothers acquired their holdings through so-called contracts for difference, which allow investors to build holdings without declaring the stake. The Reubens are understood to have taken the stakes as investments but have not ruled out becoming involved in a break up. Yesterday Whitbread’s shares rose 20.5p to 996.5p - the best performer in the FTSE 100 - after Numis Securities upgraded the company to "buy" with a £12 target price. Numis said that the group would have to extend its restructuring programme to stave off a break-up bid.