It would not be impossible but it would be difficult. I know a bloke who had a career in TV and became a barrister in his late forties, but he did not stay at the Bar for long. I know two people who started at the Bar rising forty and are now in Silk.
Age discrimination is unlawful, but it is hard to prove. People can always find a plausible reason for preferring the younger candidate.
Could you afford to live on a low income for several years? If you could obtain a tenancy, it would probably take you a while to get going in practice. Do you have a stellar academic profile? You would have to persuade chambers that you are a better bet than the 25 year old with a First in Law from Cambridge and an LLM from Harvard.
In your favour, life experience is valued at the Bar. A barrister's main sellable commodity is judgment.
It is perhaps odd that barristers should think about the posterity of their chambers, because our businesses are personal and we can never cash out, but we do think of the future of our chambers, and some (not I) might say "we want someone who will be here for the next half century, not someone who will be here for maybe fifteen years or so".