There are currently two ways of managing the treatment of men who have had a radical prostatectomy. The first option is to give radiotherapy immediately after surgery to everyone. Researchers know from several large studies that giving radiotherapy to everyone immediately after surgery will halve the risk of the PSA rising again. This means that only half of the men who have radiotherapy benefit from it. Unfortunately they don’t know which men benefit from radiotherapy and which don’t. It would be simple to give everyone radiotherapy if there were no side effects but many men experience unpleasant side effects. The second alternative is to watch men very closely (“active surveillance”) with regular clinic visits and regular PSA blood tests. The PSA blood test can detect activity of the cancer months or years before other tests and usually long before any symptoms appear. Radiotherapy is only given if the PSA starts to rise. In this situation nearly half the patients would be spared the possible side effects of radiotherapy. It is not known whether these two ways of managing the treatment of men with high risk features are the same in controlling the PSA in the long term. In one group of men radiotherapy is given to everybody with high risk features after surgery whereas in the other group radiotherapy is only given if the PSA starts to rise. The aim of the study is to therefore see whether patients treated with active surveillance (and giving radiotherapy as soon as the PSA rises) is as good as immediate radiotherapy. This study will also compare the side effects occurring in each treatment group and what affect the treatments have on quality of life. It will also compare whether the 2 ways of managing the treatment of men with high risk features results in the same percentage of men who are alive and without prostate cancer.