First Passport as naturalised citizen - when to expect documents return including my foreign passport?

Applied by paper application, went to the Post Office and paid for them to check the application and send it by special delivery. Ticked the box on the application saying that I want my documents to be returned by special delivery rather than 2nd class. Documents that I sent were my EU passport and my naturalisation certificate.

I know that approximate time to receive new passport is about 3 weeks, but what about the documents that I sent? Will they be returned sooner? If someone did this same thing recently, please share.