It's easy
All he has to do is talk to Sir Graham Brady and Sir Ian Duncan Smith and Steve Baker and all the Tory MPs who are currently fuming at the authoritarian attacks on our freedom and human rights that are the covid restrictions.
They will of course instantly understand that backdooring encryption is also an attack on our liberty and rights, and will organise a rebellion to ensure that any proposal to backdoor encryption will never get through Parliament.
Won't they?