If the Crown Court has made a hospital order under section 31, it can also impose a 'restriction order'. This means that you can only be discharged, transferred or given Section 17 leave with permission from the Ministry of Justice.
The Court will make a restriction order if it thinks it is necessary to protect the public from serious harm.
There is no fixed time limit for how long you can be kept undet this section. It changes the time limit of Section 37.