If the other prisoners attacked and killed him, I would think it served him right. I still don't think that the UK should bring back the death penalty. The countries that still have the death penalty and use it the most aren't countries that I would want to emulate, e.g. China, Saudi Arabia, Iran and the USA.
There have been numerous miscarriages of justice over the years that would have resulted in innocent people being killed by the state if the UK had still had the death penalty. It's barbaric and we are better than that as a country.