It has been a long time since the London Marathon men’s winner ran slower than the Boston Marathon men’s champion.

_• Boston 2011: Geoffrey Mutai ran 2:03:02, which was the fastest marathon ever at that time.

_• London 2011: Emmanuel Mutai won in 2:04:40. So Boston’s winning time was 1:38 faster. In every other year since, London’s winning time has prevailed.

Why it’s so rare

London’s course is flat and looped, its competition is paced. Those two factors make London faster. Boston only beats London when conditions are perfect, like the big tailwind in 2011.

For comparison:

_• Boston 2025: John Korir won in 2:04:45

_• London 2025: Sabastian Sawe won in 2:02:27

On the heels of John Korir‘s 2:01:52 course record last Monday in Boston, the men of London will be hard pressed to run quicker. Though the firepower is on hand to do that, and even more.

The late Kelvin Kiptum‘s world record of 2:00:35 from Chicago 2023 remains the world standard, and his 2:01:25 from London earlier that year sits as London’s top time ever.

With so many powerful runners lining up this Sunday in London, the potential for something special is not idle conjecture — though the margins at this level are unforgiving.

London is one of several courses where historic performances have been achieved. (see list below)

The one caveat is London’s ∼20 turns. Though many of London’s turns are gentle bends, each sharp corner forces a micro-deceleration and re-acceleration. Studies put the cost at ∼0.5 – 1.0 second per 90-degree turn at 2:50/km pace. It’s not a major time expense, but each one adds precious seconds to total time.

Below is a chart showing what an even-paced 2:00:00 marathon looks like, and Kelvin Kiptum’s world record splits.

London Forecast

The Good news:

_• Temp: Forecast – 48-50°F climbing to 13-15°C / 55-59°F by mid-morning

_• Conditions: Some clouds, light breeze.

Kipchoge’s INEOS 1:59 Challenge was 48°F. Kiptum’s 2:00:35 in Chicago was similar

_• Rain: Only 10% chance, likely dry

_• Clouds: Overcast/partly cloudy

The headwind issue

_• Miles 1-6 & 12-18: Miles 1-6 out of Greenwich and 12-18 along the Highway to Canary Wharf run straight into a forecasted 9-10 mph ENE wind for ∼12 miles total. That’s significant for any record attempt — at 2:50/km, a 10 mph headwind = ∼2-3 sec/km — though pacers will help shield the favorites.

_• Miles 6-12 & 18-23 will offer a tailwind, but you never make up downwind what you lose upwind.

_• Net effect: Forecasters say it “shouldn’t be strong enough to impact performances” for the masses. But a 10 mph headwind for half the race will likely exact a toll on the pros.

Context vs. other fast days

_• Vienna exhibition 2019: Near-zero wind. Kipchoge ran 1:59:40 (not record eligible)

_• Chicago 2023: Light wind. Kiptum ran 2:00:35

_• London 2023: “Light breeze”. Kiptum ran 2:01:25

_• London 2026 forecast: ENE 9-10 mph is stronger than 2023’s “light breeze”

Bottom line: Temp/clouds are perfect. The ENE headwind is the only negative vs. a record day. If it drops to 5 mph or shifts more north, they will have near-ideal conditions, like in Boston. If it holds at 10 mph, pacers can still hold 2:50.6/km, but it’ll cost the field some measurable time.

This is why world records are so rare and precious. You not only require the right athlete, in the right condition, led by the right pacers, but the right weather, too. And unless they start doming these courses and controlling conditions outright, records will always be catch as catch can.

Consider this: John Korir’s Boston performance represented a 0.95% improvement over the previous course record — a historically dramatic leap by any measure.

But even if we apply that same rate of improvement to London’s course record of 2:01:25, we still only arrive at 2:00:16 — inside Kiptum’s world record, but still 16 seconds shy of the two-hour barrier. So, even a Boston-scale miracle, on a headwind day, doesn’t get you sub-2.

The question becomes, how lenient will the marathon gods be this Sunday? Should be very fast, nonetheless. And probably a fairly spirited battle at that. Certainly, a fun finish to a special week for marathon fans of the world.

SITES WITH MOST WORLD RECORDS

Berlin Marathon: The record factory. 12 total: 8 men’s + 4 women’s WRs since 1998. Last: Tigist Assefa 2:11:53 in 2023

Polytechnic Marathon (London): Historic race, running 1909-1996. Site of 8 IAAF world records, 1909-1965

London Marathon: 7 WA-recognized records. Last: Mary Keitany 2:17:01 women’s-only WR in 2017

Chicago Marathon: 5 WA-recognized records. Currently holds both men’s + women’s WR: Kiptum 2:00:35 (2023) & Chepngetich 2:09:56 (2024)

New York City Marathon: 5* WA-recognized records, but 4 disputed due to short course in 1978-1981

*Boston has 3 WA-recognized records. Last: Joan Benoit 2:22:43 in 1983. But since 1990, Boston has been ineligible for record purposes due to its net downhill, point-to-point course.

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