This is why briefcases are crap - trivial to nick.
Rucksacks are so much better because you don't have to put them down to do common stuff like buying a ticket.
Papooses are best, as they are always in front of you so can't be surreptitiously picked like a rucksack can.
Solved - all serious businessmen carrying important stuff should be using a papoose. It won't look daft if everyone does it, right?