serial killer Dennis Nilsen spoke of his remorse for his grisly murder spree – and felt guilty for smiling.His terrible crimes have been made into new ITV drama Des, starring David Tennant, which will begin next week.In a 2014 letter from his cell at Full Sutton prison in Yorkshire, he discussed a visit made to US jail Alcatraz and wrote: “Well you say it costs $15 to visit Alcatraz."The price of my permanent visit to Full Sutton has been much higher than that – in terms of the cost of the lives