That 40% stake in Cellnet Mobile Communications Ltd is becoming a boon to Securicor Group Plc, helping the company to a pre-tax improvement of 34% at UKP63m for the year to September. The Cellnet contribution to that was UKP46.3m, but that was up under 1% because of heavy investment in the new Lifetime cellular service in the first half. Cellnet remains less profitable than rival Vodafone Group Plc, but it is becoming ever more the tail wagging the Securicor dog, and increasingly a reason for investors in telecommunications to buy the shares.