London Heathrow Duty free selling duplicate liquor?

Hey, I was wondering if anyone else has had the same experience related to buying liquor from the duty free. I bought a 12 year Macallan for my dad from London Heathrow Duty free which burned a 70 pound hole in my pocklet. However on opening it, it smelled and tasted very basic. Now i’m no whiskey expert but my dad is quite a bit more experienced and he said it absolutely isn’t what I paid for.