Finally, he apparently wanted to relax in the nest and made his round-about way down. However the reception he received from the other two birds was vicious!
They squawked, flapped their wings and made it quite plain that they did not want him back. He kept retreating and then returning but got the same hostile treatment each time. One of the other two eventually decided to climb up the tree too and disappeared in the ivy round the back. I could just see more friction taking place between this one and the first climber- more flapping wings and outstretched necks.
Finally- after nearly five hours there!- I had to leave. The ostracized one had retreated to a high position on the tree, the second one was stilllurking in the ivy while the third one was standing uneasily in the nest... It will be interesting to see what happens next!