Last year I chatted with a PhD graduate about their viva prep.
In her department they encouraged final year students to give a seminar about their PhD. As the viva approached they would deliver a talk summarising their research and then take questions. For the graduate I spoke to this was a hugely helpful practice: she got to spend time thinking about how to communicate her work, an opportunity to practice talking about what she had done, and lots of chances to answer unexpected questions from her audience. Three things that are perfect preparation for the viva.
A great idea. At the time I heard the story I thought, “I wish my department had suggested we do this.” A while later I realised, “If it had occurred to me, I could have just done it.”
And so could you. You don’t need permission, you just need a room. Find a space, invite some people, share your work, prepare for your viva.