10miles
Solo · 1 lap · Day
Grimsthorpe Castle · 22 & 23 May 2027
Four solo distances, a 100-mile relay and a night 10 on a stunning castle estate in South Lincolnshire. All abilities, a friendly vibe, and a 4.9-star rating from the people who have run it.
4.9★
On Let's Do This
320+
Runners in 2025
10mi
The loop
550ft
Climb per lap
6
Ways to race it
Choose your distance
Every race runs the same 10-mile loop around the Grimsthorpe estate. Pick the distance that suits you, from a first trail 10 to the full 100.
Solo · 1 lap · Day
Solo · 1 lap · Night
Solo · 4 laps
Solo · 7 laps
Solo · 10 laps
Teams of up to 5 · 10 laps
All finishers receive a medal. Trophies for first, second and third male and female in every solo race, and for the winning relay team. You can't change distance after entering, and dropping down mid-race counts as a DNF.
10-mile loop · 550ft per lapThe course
The route is a 10-mile loop that covers beautiful grass trails through ancient woodland, limestone tracks, quiet estate roads and a stretch along a disused Victorian railway line. It skirts the estate lake before reaching the start and finish in front of the castle itself.
It's undulating with no major hills, which makes it ideal for a first ultra, a step up in distance or a PB attempt. The course is fully marked.
The new Grim Reaper
The Grim Reaper was relaunched in 2023 by Steve Cole and Laura Bailey, runners local to the Grimsthorpe Estate. Their plan was simple: an event that caters for runners of all abilities, in a stunning location, with a friendly, supportive vibe.
Judging by the 4.9 out of 5 rating from the 320+ runners who took it on in 2025, it's working. Bog Dog Running, Stamford's specialist running shop, is behind the event, so there's a well-stocked running shop on site should you forget anything.
Need to know
Kit, rules, cut-offs and the small print. Read it once now so race weekend is all about the running.
Grimsthorpe Castle, Bourne, PE10 0LY · grimsthorpe.co.uk
Saturday 22 May 2027
The 70 and 100-mile races have a strict cut-off of 28 hours. The 40-mile race has a strict cut-off of 27 hours.
Mandatory kit applies from 6pm. Before 6pm you are free to carry what you want. Everyone starting a lap after 6pm MUST be carrying all mandatory kit, and we will be checking anyone we feel isn't carrying the right gear.
There will be a well-stocked running shop on site should you forget anything.
Cupless race: bring your own cup. Cups will be available to buy on the day.
Ultra-distance runners are expected to be self-sufficient and manage their own supplies. You are welcome to bring a tent or shelter to set up near the start and finish.
There is an aid station at mile 5 stocked with limited snacks and water, with a toilet alongside it.
Hot food and hot and cold drinks are available to buy at the start and finish from 8am until 2pm on Saturday.
Fully qualified medics are on site throughout the event.
Permitted from mile 50, on foot only, one pacer per runner at any one time. Runners are responsible for the actions of their pacers.
You are welcome to walk the whole course, but a crew point is only permitted at the start and finish. Anyone found breaking this rule will be disqualified.
Entry to the estate is £5 per adult and £2.50 per child, 100% of which goes to the Grimsthorpe & Drummond Castle Trust Limited (registered charity 507478). Walk the whole course to cheer runners on, grab food and drink, and the adventure playground will be open.
Runners are permitted to camp on site on the Friday and Saturday nights. The camp area is close to the start and finish line, making it ideal for storing supplies for the race.
Strictly no fires or BBQs.
There's no official qualification standard, but we suggest:
Not sure? Pop into the shop in Stamford and talk it through with us.
If you need to withdraw for any reason we are unable to offer a refund. You can defer your place to 2028 up to four weeks before the race (23 April 2027). After this our race-day costs, which are based on numbers, have been incurred.
You can also transfer your place to another runner: email hello@bogdogrunning.co.uk with their details. Transfers after 26 April incur a £5 admin fee.
Should the 2028 event not go ahead due to unforeseen circumstances, your deferral is void and no refunds will be given.
You cannot change the distance you selected on entry. Enter the 100 and stop at 70 and you're a DNF; enter the 70, finish and feel good, and you can't upgrade to the 100.
I accept the following terms for my own entry. I also accept the terms on behalf of any other participants I am entering in this event, all of whom have been provided with a copy of these terms and accept them: I declare that the information I give is complete and correct. I understand and agree that I participate in this event at my own risk and that I must rely on my own ability in dealing with all hazards. I am aware that the function of the marshals is only to indicate direction and that I must decide if the movement is safe. I agree that no liability whatsoever shall be attached to the promoter, promoting club, meeting sponsor(s) or member of the promoting club in respect of any injury, loss or damage suffered by me on or by reason of the event, however caused. I consent to publication of my name, club, race category, race number, finishing time and race position in race pre-entry and results lists.