The government has changed its plan to release thousands of offenders in England and Wales well before the end of their sentences in an attempt to make space in prisons. People sentenced for rape, serious child sex and grooming offences will now not be eligible for early release from October. But some prisoners who are not excluded could be freed after serving a third of their total custodial sentence rather than after 40% or 50% of their term. This is not the first time a government - Conservative or Labour - has had to release prisoners early to make space in England and Wales' overcrowded prisons. BBC Verify has looked at the reasons why ministers feel the need to resort to these measures.