How do you unlock harry lake task on Lego Harry Potter?

You can't unlock a "Harry Lake" task in Lego Harry Potter. There is no character named Harry Lake in the Harry Potter universe, and therefore no corresponding task in the games.

It's possible you're thinking of a different character or task. Could you clarify:

* Which Lego Harry Potter game are you playing? (e.g., Lego Harry Potter: Years 1-4, Lego Harry Potter: Years 5-7)

* What is the specific task or character you're looking for?

Once I have this information, I can help you find the solution!