2026 Two Tunnels Marathon - Aug 16 Countdown

Q: What is the Two Tunnels Marathon route?

The Two Tunnels Marathon starts and finishes at Brickfields Park, Bath (BA2 1LX) and runs two off-road laps of the Two Tunnels Greenway. Each lap heads up a slight gradient through the 408m Devonshire Tunnel and the 1,672m Combe Down Tunnel - the latter with its own sound-and-light installation - then follows the Kennet & Avon Canal towpath through the Limpley Stoke valley, riverside paths past old warehouses, and into the World Heritage city centre past Bath Abbey and Pulteney Weir. It is run by Relish Running Races and billed as the foot race with the longest underground section in Britain.

Q: Is the Two Tunnels Marathon flat? How hard is it?

It is mostly flat off-road but not a pancake-flat road course. Built on old railway grade, the route has gentle rises rather than steep hills - roughly 250m of total ascent across the two laps, rated moderately undulating. The off-road surface, two laps and city-centre road crossings mean most runners finish a little slower than their flat-road marathon time, but it is far quicker than a true hill or trail marathon. Plan your effort with our pace calculator and preview the gentle climbs with our elevation profile tool.

Q: How long are the tunnels and what is it like running through them?

You run through two reopened Victorian railway tunnels twice - the Devonshire Tunnel (408m) and the Combe Down Tunnel (1,672m), which is long enough that organizers bill the race as having Britain's longest underground section. Both are well lit and well surfaced, with Combe Down featuring a sound-and-light art installation. They run cool and damp, so it takes a few seconds for your eyes to adjust - the organizers ask you not to wear sunglasses inside and to keep left as the path is shared with the public.

Q: What shoes should I wear and what is the surface like?

The course is off-road but on a well-surfaced shared-use greenway - compacted former railway path, canal towpath and some tarmac through the city, rather than mud or technical trail. Either trail shoes or normal road trainers work fine; you do not need aggressive lugs. Note that in-ear and over-ear headphones are banned under UK Athletics rules on this course (only bone-conduction headphones are allowed) so you can hear marshals, cyclists in the tunnels and traffic at road crossings.

Q: How do I enter the Two Tunnels Marathon 2026, and how much is it?

The full marathon is held on the August race date (Sunday 16 August 2026) - the June and February editions are half marathon and shorter only. Entry is open to the public online via the official site (bathmarathon.com / relishrunningraces.com), with no ballot, a marathon fee of around 60 GBP and a minimum age of 18. The marathon runs in timed waves and is capacity-limited, so book ahead. The race weekend also features a 50K ultra, half marathon, 10K, 5K and the family Colourburst.

Q: What time does the Two Tunnels Marathon start and what is the cut-off?

The marathon sets off in waves from 10:00 on Sunday 16 August 2026 at Brickfields Park. The key cut-off is a lap gate: you must reach the half-marathon/marathon split (around 13.2 miles) within 3 hours of your start, or you are switched to the half-marathon distance and given a half medal. With the 10:00 start that puts the practical overall limit at roughly 6 hours. Because of the multi-wave format, runners moved to the half do not receive a finish time.

Q: Is the Two Tunnels Marathon a Boston Qualifier?

No. Although Relish measures the course accurately with a measuring wheel, it is an off-road, two-lap route on a public greenway with live road crossings and no road closures, not a UK Athletics road-certified race, so a Two Tunnels finish is not valid for Boston qualifying (BQ) or a London Good For Age (GFA) entry. GPS watches also misread distance in the tunnels. Come for the tunnels, the canal and the city, not a qualifying time. If a standard is your goal, check it with our Good For Age tool and pick a certified road race instead.

Q: How do I get to the Two Tunnels Marathon, and where do I stay?

Brickfields Park sits in southern Bath with zero on-street parking for runners - drive to the Odd Down Park & Ride (BA2 8PA) and take the event TT1 bus (about 15 minutes, ~4.50 GBP return). By train, Bath Spa is the main station (about 1.5 miles away) and Oldfield Park is closer (about half a mile, signed to the start). Bath is a compact World Heritage city with plenty of hotels, B&Bs and guesthouses; book early, as August is peak tourist season.

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Race Information

Race	2026 Two Tunnels Marathon - Aug 16
City	Bath
Date	2026-08-16 at 10:00
Time Limit	6 hours
Cutoff pace	8:32/km
Timezone	Europe/London
Official Site	Relish Running Races
Registration	Register · 60 GBP

Race Day Weather

Average Temperature	16.9°C / 62°F
Humidity	81%
Wind	24.4 km/h
Rain Chance	46%
Typical Conditions	A mild late-summer morning in the sheltered Avon valley around Bath. Expect around 15-18C (59-64F) at the 10:00 start, climbing toward the low 20s by early afternoon, with fairly high humidity and a real chance of a passing shower - mid-August here is pleasant but rarely guaranteed dry. The two long railway tunnels stay cool and damp year-round, a welcome few minutes of shade on a warm day.

What to Prepare: Dress for mild summer running and pack a light waterproof - Bath weather can turn quickly. Do not wear sunglasses in the tunnels and avoid in-ear headphones (only bone-conduction is allowed, so you can hear marshals and cyclists). Trail shoes or road trainers both work on the well-surfaced greenway. Do not trust your GPS distance - the tunnels scramble the signal, so run by effort and the mile markers, not your watch.

Based on historical averages for race week. Use our Weather Score Calculator and What to Wear Guide for personalized advice.

Wind Impact on Race Day

Wind at 24.4 km/h can affect your marathon pace by 5-15 seconds per kilometer. Headwinds slow you down exponentially — a 20 km/h wind costs more than twice a 10 km/h wind.

Calculate your wind-adjusted pace →

Race-Week Climate

Based on 20 years of race-week weather (2005-2024), MERRA-2 reanalysis

	Cooler	Typical	Warmer
Temperature	14.7°C	16.7°C	19.1°C
Dew point	10.6°C	13.1°C	15.7°C

Wet-day chance: 46% Runnability: 68/100

Data: NASA POWER (MERRA-2 reanalysis), NASA Langley Research Center

Course Profile

Course Type	Two off-road laps from Brickfields Park through the Two Tunnels Greenway, canal towpath and Bath city centre
Elevation Gain	250m
Terrain	Mixed
Profile	Mostly flat off-road on old railway grade, with gentle rises rather than real hills - roughly 250m of total ascent across the full two laps, rated moderately undulating. Each lap climbs a slight gradient up to the 408m Devonshire Tunnel and the 1,672m Combe Down Tunnel, then runs the Kennet & Avon Canal towpath, riverside paths past Bath Abbey and Pulteney Weir, and city-centre streets. Faster than a hill marathon but not a flat road PB course.

Prepare for 2026 Two Tunnels Marathon - Aug 16

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Grade Adjusted Pace (GAP) Calculator — Hills & Strava

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Frequently Asked Questions

What is the Two Tunnels Marathon route?

The Two Tunnels Marathon starts and finishes at Brickfields Park, Bath (BA2 1LX) and runs two off-road laps of the Two Tunnels Greenway. Each lap heads up a slight gradient through the 408m Devonshire Tunnel and the 1,672m Combe Down Tunnel - the latter with its own sound-and-light installation - then follows the Kennet & Avon Canal towpath through the Limpley Stoke valley, riverside paths past old warehouses, and into the World Heritage city centre past Bath Abbey and Pulteney Weir. It is run by Relish Running Races and billed as the foot race with the longest underground section in Britain.

Is the Two Tunnels Marathon flat? How hard is it?

It is mostly flat off-road but not a pancake-flat road course. Built on old railway grade, the route has gentle rises rather than steep hills - roughly 250m of total ascent across the two laps, rated moderately undulating. The off-road surface, two laps and city-centre road crossings mean most runners finish a little slower than their flat-road marathon time, but it is far quicker than a true hill or trail marathon. Plan your effort with our pace calculator and preview the gentle climbs with our elevation profile tool.

How long are the tunnels and what is it like running through them?

You run through two reopened Victorian railway tunnels twice - the Devonshire Tunnel (408m) and the Combe Down Tunnel (1,672m), which is long enough that organizers bill the race as having Britain's longest underground section. Both are well lit and well surfaced, with Combe Down featuring a sound-and-light art installation. They run cool and damp, so it takes a few seconds for your eyes to adjust - the organizers ask you not to wear sunglasses inside and to keep left as the path is shared with the public.

What shoes should I wear and what is the surface like?

The course is off-road but on a well-surfaced shared-use greenway - compacted former railway path, canal towpath and some tarmac through the city, rather than mud or technical trail. Either trail shoes or normal road trainers work fine; you do not need aggressive lugs. Note that in-ear and over-ear headphones are banned under UK Athletics rules on this course (only bone-conduction headphones are allowed) so you can hear marshals, cyclists in the tunnels and traffic at road crossings.

How do I enter the Two Tunnels Marathon 2026, and how much is it?

The full marathon is held on the August race date (Sunday 16 August 2026) - the June and February editions are half marathon and shorter only. Entry is open to the public online via the official site (bathmarathon.com / relishrunningraces.com), with no ballot, a marathon fee of around 60 GBP and a minimum age of 18. The marathon runs in timed waves and is capacity-limited, so book ahead. The race weekend also features a 50K ultra, half marathon, 10K, 5K and the family Colourburst.

What time does the Two Tunnels Marathon start and what is the cut-off?

The marathon sets off in waves from 10:00 on Sunday 16 August 2026 at Brickfields Park. The key cut-off is a lap gate: you must reach the half-marathon/marathon split (around 13.2 miles) within 3 hours of your start, or you are switched to the half-marathon distance and given a half medal. With the 10:00 start that puts the practical overall limit at roughly 6 hours. Because of the multi-wave format, runners moved to the half do not receive a finish time.

Is the Two Tunnels Marathon a Boston Qualifier?

No. Although Relish measures the course accurately with a measuring wheel, it is an off-road, two-lap route on a public greenway with live road crossings and no road closures, not a UK Athletics road-certified race, so a Two Tunnels finish is not valid for Boston qualifying (BQ) or a London Good For Age (GFA) entry. GPS watches also misread distance in the tunnels. Come for the tunnels, the canal and the city, not a qualifying time. If a standard is your goal, check it with our Good For Age tool and pick a certified road race instead.

How do I get to the Two Tunnels Marathon, and where do I stay?

Brickfields Park sits in southern Bath with zero on-street parking for runners - drive to the Odd Down Park & Ride (BA2 8PA) and take the event TT1 bus (about 15 minutes, ~4.50 GBP return). By train, Bath Spa is the main station (about 1.5 miles away) and Oldfield Park is closer (about half a mile, signed to the start). Bath is a compact World Heritage city with plenty of hotels, B&Bs and guesthouses; book early, as August is peak tourist season.