A chap takes the trouble to study form and saves up his pocket-money to have a bet on a good thing

“A chap takes the trouble to study form and saves up his pocket-money to have a bet on a good thing, and then he goes and gets let down like this. It may be funny to you, but I call it rotten.
And another thing I call rotten is you having kept it from me all this time that you were.
'Young Porky’, pa.”
(a) Who is speaking to whom?
(b) What does ‘let down’ mean in the above passage?
© What is the irony here?

(a) Harold is speaking to his father.
(b) ‘Let down’ in the above passage means ‘disappointed’.
© It is ironical that though Harold was fond of boxing celebrities, the fact that he himself was the son of a boxing celebrity was kept hidden from him.