Further advance on main mortgage as deposit for holiday property

If I obtain a further advance on my main property to help fund the purchase of a holiday property (to be used as a holiday let meeting requirements as stated by HMRC), is the interest on this borrowing an allowable expense? In short, do you have to get a specific holiday let mortgage or loan for the interest to be used as an expense or doesn't it matter where the loan money comes from?

Hi Sarah Wise,
No this is not allowable as the mortgage is not against the rental property.
Thank you.