When we called in our locksmith to change the locks on the flat, he took one look at our back door and said "This is an internal door! I could kick this down in less than five seconds".
So we promptly got it replaced!
With a very plain, unpainted, wood, block-like door.
After a little too long leaving it untreated and rained on, I finally gave it an undercoat last week. Then decided it was far too boring being white... so raced out to the hardware store and bought a half litre tin of bright red.