1. Do your novel thinking outside your writing time so when you get the chance you know roughly what you're going to write.
2. If you say something like, "I just want to do some writing, could you keep an eye on the children", you're in effect asking for permission. Sneak off without telling anyone and I bet it'll be ten minutes at least before anyone notices you've gone.
3. Leave your writing with a few notes about where you're going next. When you next get the chance they'll refresh your memory quickly so you use the time effectively.
4. If you get stuck on one section jump to the next bit you fancy writing; you can always go back later and fill in the gaps.
5. Give up watching television. Or Sudoku, the crossword, emails, Twitter - there are thousands of things that gulp down novel writing time. And if all else fails...
6. Cultivate a reputation for IBS. Why not? Who will ever question, other than sympathetically (or possibly cautiously), the time you're spending in the loo?
If you really, really want to write a novel you'll find those ten minutes. It's just about the maths. A x B = C. That's all you need to know.
* As a guideline, this post is 300 words.