When Alf gets stuck inside the wardrobe he is moving for Mrs Hollingbery he overhears her telling Mrs Carey she only wanted to marry him for his money so he takes all the cash he has been hoarding to the bank. The notes are so old they are no longer legal tender and having accumulated so much undeclared cash might cause problems with the tax office. Fortunately Alf sees a way round such matters. (thetvdb.com)