In David Copperfield, Chapter 12, why did David decide to run away from London?

David Copperfield at this stage of the novel has been sent by his stepfather, Mr. Murdstone, to work in his wine warehouse under terrible conditions. However, he is lodging with the Micawber family, which starts his longstanding relationship with them and their pecuniary difficulties. David finds solace in their friendship, however his feelings of abandonment and loss of status still cause him some misery. Mr. Micawber is put in debtor's prison and after his release the family decides that they are going to move to look for work. David decides at this stage that he will not stay in London without the Micawber family and thus borrows money from Peggoty and flees to cast himself upon his Aunt, Betsy Trotwood.