How old was Charles Dickens when he wrote Oliver Twist?

Dickens wasn't the kind of writer who would work on one project until completion, then move on to the next. He usually skipped from one to the other depending, probably, on things like inspiration, research and personal whim. Most of his output appear in serial form and Dickens seldom finished the story before it began to be published. It's probably just a side benefit, but the reading audience actually influenced the outcome of some stories. We do know that Oliver Twist, his second book and one of the better known, was first published in Bentley'sMiscellany as a serial, in monthly installments that began appearing in the month of February 1837 and continued through April 1839.