Private client stockbrokers are enthusiastic about the shares' prospects and believe investors should pay up rather than cash in.
Eric Hathorn of Henderson Crosthwaite said: 'The shares have done what we hoped they would - provide a good dividend stream for income. But in 1995 the regulators will look critically at any company where the return on capital in uncomfortably high. Manweb and Yorkshire look vulnerable.'
Charles May at Wise Speke, Tony Richards of Quilter Goodison and Keith Loudon of Redmayne Bentley also believe that it is a good idea to hang on to the shares.
Mr Richards favours London and Yorkshire, but would recommend all share holders to pay up. Mr Loudon points out that employees need to hang on until after the call to get all their perks.
After Friday the shares will trade in their fully-paid form with the final instalment due on 15 September.