Optimising RT dose for anal cancer - the development of three clinical trials in one platform by Sebag-Montefiore, D, Adams, R, Bell, S, Berkman, L, Gilbert, D, Glynne-Joones, R, Goh, V, Gregory, W, Harrison, M, Kachnic, L, Lee, M, McParland, L, Muirhead, R, O'Neil, B, Hutchins, G, Rao, S, Renehan, A, Smith, A, Velikova, G, Hawkins, M