The Big Half 2026: Complete Guide to London's Half Marathon

On September 6, 2026, over 15,000 runners will toe the line at The Big Half, one of London's most vibrant half marathons coursing through four boroughs – Tower Hamlets, Southwark, Lewisham, and Greenwich. First held in 2018, this race starts at Tower Bridge and finishes by the famous Cutty Sark in Greenwich. A closed-road course that shows you London from a different angle.

The Big Half by numbers

Distance: 21.1 km (half marathon) Elevation gain: 80 m Date: Sunday, September 6, 2026 Location: London, United Kingdom Start: The Highway, north side of Tower Bridge Finish: Cutty Sark, Greenwich Start time: 8:30 AM Entry fee: £16-60 depending on registration window Course type: Road, closed to traffic Course records: Men: 1:00:22 (Kenenisa Bekele, 2020) / Women: 1:07:35 (Eilish McColgan, 2022)

Organised by London Marathon Events, the race attracts both elite runners and mass participation. The event also features The Big Relay (teams of four) and The Big Mile for families.

Course breakdown

Km 0-3: Start and the Limehouse tunnel

The start is on The Highway, north of Tower Bridge, then you head east towards Canary Wharf. But quickly, just over a kilometre in, you plunge into the Limehouse Link tunnel for about 1.8 km underground.

This is a unique section: no spectators, a slightly eerie atmosphere. The tunnel descends first, then climbs back up – resist the urge to attack the downhill too hard because you'll have to climb the same distance back up. Your GPS will completely lose signal. At the tunnel exit, around mile 2 (km 3), you face the first small climb.

Km 3-8: Canary Wharf loop and return

Around kilometre 5, you reach Canary Wharf and turn around to head back towards Tower Bridge. At mile 3, entering the Canary Wharf area, you encounter a second small rise. The skyscrapers can also disrupt your GPS signal.

You then pass back through Wapping before crossing Tower Bridge – one of the race highlights, around kilometre 11, one of the best sections of the course.

Km 8-16: From Bermondsey to Deptford

Once across Tower Bridge, you head south through Bermondsey, Rotherhithe, Surrey Quays, then Deptford. The course generally follows the curves of the Thames. This is a long section, with stretches in Lewisham that provide little in the way of visual distraction. The terrain stays flat but effort starts to build. The neighbourhood atmosphere and crowd support carry you through.

Km 16-21.1: Final kilometres to Greenwich

The final mile or so, entering Greenwich and approaching the Cutty Sark, is an unforgettable experience. The finish line sits right next to the iconic Cutty Sark ship. Finish facilities are located in Greenwich Park. You complete the race on an overall flat profile, with only 80m of cumulative elevation gain throughout.

What weather to expect

For early September in London, you can expect typical late-summer conditions: maximum temperatures around 23°C, minimums near 14°C in the early morning. Roughly 40% probability of rain on the day (average calculated from past years), with about 2.8mm of average precipitation. Average wind around 17 km/h.

Plan for light kit (vest or technical tee), but keep something to stay warm before the start if you get cold easily. With an 8:30 AM start, temperatures will still be cool. If weather forecasts show rain, a cap and moisture-wicking clothing will make the difference. Hydrate from the moment you wake up – 23°C can dehydrate you quickly during effort.

Race strategy and tips

Managing the tunnel and early miles

The Limehouse tunnel is a classic trap. Start-line adrenaline pushes you to charge down the descent. Resist this temptation. Without GPS and without visual cues, you risk losing your rhythm. Keep a steady pace, rely on feel and heart rate. The climb back up comes fast.

Don't be fooled by the "flat" profile

At 80m elevation gain, The Big Half is objectively flat. But the two small rises at km 3 and 5, just after the tunnel and entering Canary Wharf, can surprise you if you've gone out too hard. Keep something in reserve in the early kilometres to handle these slight slopes without breaking your rhythm.

Nutrition and aid stations

Plan your hydration strategy ahead, as aid stations at this type of London event are well-organised but sometimes spaced out. Carry a gel or two if you're chasing a time, taking them around km 10 and km 16. Drink regularly from the first stations to avoid getting behind.

The tough section: km 12-18

The long stretches in Lewisham offer little visual distraction. This is where it can get mentally challenging. Break this section into 2km segments. Focus on the crowd support, which is strong in these popular neighbourhoods. Stay in your rhythm, don't let yourself drift.

What makes this race special

The Big Half celebrates London's diversity and the energy of the four boroughs it passes through. Each borough has its own identity, atmosphere, and community cheering you on. The closed-road course gives you rare access: running through the heart of London on roads normally choked with traffic.

The Limehouse tunnel, closed to cars for the occasion, is an experience in itself. Running underground for nearly 2km in a space normally forbidden to pedestrians is unique. Crossing Tower Bridge at km 11, with its iconic towers, remains a standout memory.

Practical info: Bib collection typically takes place in the days before the race. Participants are encouraged to use public transport to reach the start area (Tower Hill, Fenchurch Street stations). The finish village is set up in Greenwich Park.

Getting encouragement during The Big Half with Cobbr

Kilometres 12 to 18, through the long stretches of Lewisham and Deptford – that's where fatigue sets in. It's also where a voice message from your loved ones can change everything. With Cobbr, your family and friends record encouragements that automatically trigger at the kilometre they choose. At km 15, when the finish line still seems far, hearing your brother's voice or your best mate's gives you an unexpected boost. They don't need to be there in person – their voices run with you.

The Big Half FAQ

What is the distance of The Big Half?

The Big Half is a half marathon of 21.1km, from Tower Bridge to Greenwich.

Is it a tough course for a first half marathon?

With only 80m of elevation, it's an accessible course. The small rises after the Limehouse tunnel (km 3-5) require pace management, but nothing insurmountable for a prepared runner. The atmosphere really carries you.

Are there time cutoffs?

Specific information on time cutoffs isn't always published in advance, but London Marathon Events are known for being inclusive. Expect roughly 3 hours for course closure.

What's the weather like in early September in London?

Early September typically brings 14°C in the morning and 23°C by midday, with about a 50/50 chance of a few drops. Plan adaptable kit.

Can you receive encouragement from loved ones during the race?

Yes, even if they can't be there physically. With Cobbr, they record voice messages that trigger at strategic kilometres. Perfect for support when you need it most, like around km 15.

Do you need to be an experienced runner?

No. The Big Half welcomes runners of all levels. The course is flat, the atmosphere festive. With serious preparation (3-4 runs per week for 8-12 weeks), a motivated beginner can absolutely complete the half.

The Big Half is London running. Four boroughs, an underground tunnel, a finish at the foot of a 19th-century sailing ship. If you're looking for an urban half marathon with character and genuine atmosphere, September 6, 2026 could be your date.