Thanks for your follow up.
I made the recipe at the weekend with 1 1/2 tsps and it seemed OK. I just felt that the larger baking powder quantity would leave a taste in the cake. Anyway, it worked OK with 1 1/2 tsps but, just out of curiosity I might make it again with 2 - 3 tsps and see what happens.
I think the recipe would be American, considering its source (Facebook)