LONDON — Sixteen years ago, it was Britain that was trying to make sense of a mass shooting, with the nightly news filled with grieving relatives and old family photographs.

A 43-year-old named Thomas Hamilton was the gunman, and his killing floor was not a midnight movie showing but a primary school in Dunblane, Scotland. He killed 17 people, all but one of them children, before committing suicide.

But the reaction here could scarcely have been more different from the one in the United States to the mass shooting in Colorado. With outrage still white hot, gun opponents in Britain organized a successful campaign for a gun ban, and by the end of 1997 Parliament had outlawed the private ownership of nearly all handguns.

It is against that backdrop that Georgina Geikie, a 27-year-old English barmaid, will approach the firing line at the Royal Artillery Barracks here Wednesday. She is the first British athlete to compete in an Olympic cartridge pistol competition since 1996, and she will be doing something that is illegal for nearly everyone in the country — and until recently was illegal for her as well.