I have asked this in some other forums but did not get a conclucive answer.
Its for the protection, there would be no load at switch on, curretly the designers has used a 25A BS88 fuse . from what I have discussed with others, the inrush current would be the same but for a longer duration as there is no electrical coupling between the two transformers. i.e. the second cannot magnitize until the first has saturated.