Assemble 49 dangerous criminals who are taking up valuable cell space in our majesty's over-burdened penal system.
Give them all a numbered bib, from one to forty nine, oh, and a baseball bat each. Put them in a large futuristic arena, encouraging them to set about one another with baseball bats
Stop when you have seven left. Inform the remaining seven that the next one to fall will be the "bonus ball".
Once this happens you have the lottery numbers.
Miles more entertaining and cost effective than the way they do it at the moment.