One of the main reasons for runners presenting in my sports injury clinic is due to training error, this is linked to one of two factors, overuse and misuse.
The body is a very resilient, adaptable and robust structure and has many factors (physical, mental, hormonal, nutritional etc.) involved when adapting to load placed upon it during activities like running.
Either being too enthusiastic and running without appropriate rest, or increasing distance too soon are often the reason for developing an injury. Sometimes this increase in load can be difficult to spot, so watch out for increasing elevation profiles on similar distances, changing running surface or speed.
Your weekly mileage may remain similar but another variable can contribute to overload, keep vigilant for this. You can monitor this in a diary or on a GPS watch.
A good starting point is to determine your own skills and starting place e.g. current fitness, running technique, experience, muscular strength, time for training etc.
If you look to the 280km challenge (assuming you are not used to running these distances of brutal terrain) and work backwards, you may feel overwhelmed and lose confidence.
Start from the here and now, and work to where you need to be, this is best written down in a list to chart your progress, build confidence and commitment.
Write anything you can on the list that could be a factor in helping you (current strengths) and address any potential barriers (limitations, current physical condition etc.) such as time.
Here are some tips to help manage your initial programme