The bricks are also quite soft, yellow stocks.
Are you in London or environs by chance?
The bricks there in older houses can be relatively soft, but even allowing for soft hand-made bricks in weak mortar, a 1200 long padstone would not normally be needed in a domestic setting.
Have a look for the padstone in the PhD thesis he has sent you - there should be a load quoted for the pad somewhere around that page.