I walked for 4 minutes, ran for 1 min, along the Sihl river lap and it took me just under 20 minutes. I felt great, got some fresh air in my lungs and got my blood moving round my body. My boobs didn't leak and (ahem) my pelvic floor was also up to the task :-)
My goal? Increase my speed and gradually decrease walking and increas running. Wonder how fast I can do this lap by Christmas?