I understand that the RAF may have successfully blocked transport on rivers and canals of off-site built sections of Type-21 U-boats - is this correct, and if so can someone please let me have the details of the air raid?

Secondly, given that earlier bombing had forced Germany to make the U-boats via an offsite construction method - would it be fair to say the RAF seriously delayed the Type-21 programme and if so, by how much time?

Many thanks,
Marcus Gibson
UK journalist.