Running the London Marathon: 1 in 143,000 chance it kills you

~7 micromorts. Like cycling 410 km, or smoking 8 cigarettes. Measured.

Mortmeter: Worth it. A tiny cardiovascular toll for a shiny medal and lifelong bragging rights.

Assuming: One person completing the full 42.2 km London Marathon course

How we got this: Decades of race registries show marathon mortality sits around one death per 100,000 to 150,000 participants, mainly driven by occult cardiac conditions. That yields 1 marathon times 7 micromorts per race, giving 7 micromorts.

What gets you: Sudden cardiac arrest from undiagnosed heart defects, Exercise-associated hyponatremia from overdrinking water, Exertional heat stroke.

Cheaper version: A steady half-marathon cuts the acute cardiovascular strain by roughly 70 percent.

Sources and method: how Mortmeter prices things, and the Atlas of measured risks.

More priced risks: Sharing a bottle of Flor de Pingus, Riding Polyppen at Bakken in Denmark, Eating 2 whole pizzas, Drinking a bottle of red wine, Winter bathing in the Øresund, A week of off-piste skiing, Getting LASIK eye surgery, Texting while driving on the motorway.