'I was good at adding up' - shadow chancellor John McDonnell told Labour activists as his childhood kindness to a fellow maths scholar emerged.

The newly-appointed frontbencher retold the story of how he helped a girl at primary school with her maths answers so she did not get the cane, after reading the anecdote in the EDP letters pages.

He reflected on his childhood in Great Yarmouth and told members during the packed event how he still sails on the Norfolk Broads.

The rebel MP reflected on his reputation for 'telling it like it is' and admitted that he could be quite aggressive, but said that Jeremy Corbyn was giving him lessons in being more consensual. He told of his 'working-class' background and how he had moved from 'one of the worst slums in Europe' in Liverpool to Great Yarmouth as a child.

The former Great Yarmouth Grammar School pupil described how he worked hard at school, but had found the whole grammar school system 'appalling' with pupil tested and divided at the age of 11.

He worked his way up through the Greater London Council – where, he said, he had effectively been 'chancellor'.

Mr McDonnell described how he takes his mind off things by sailing his Skipper 17 on the Norfolk Broads, although he joked that he and his wife did tend to fall out.

'When people see us coming they get off the water. You are so terrified it takes your mind off everything.'