The first questions on an insurance proposal form are
Who is the registered keeper ?
Who is the proposer?
Who will be the main driver?
It is quite common for the registered keeper not to be the main driver , for a company car for example, but you have to be honest .
What you CAN NOT do is say that the registered keeper is the main driver when they are not.
A young driver could say that their Mum or Dad is the keeper but they are the main driver , as long as this was correct this would be legal but the insurance would be VERY high.