@amir - I wonder if our paths crossed at any point yesterday? I was doing a DIY 300, which coincidentally had 2.9km of climbing.
It was a lovely ride: down to Carnwath via Tarbrax, turning east to pick up the westerly wind, and get blown gently downhill through Peebles (timed to miss the road closures on the A72), on the lovely railway path to Innerleithen, Melrose (stopped to fill up bottles), Kelso, Coldstream and Berwick upon Tweed. NCN 1 into Berwick is a shameful embarrassment. I stopped in Berwick McDonald's for a cheeseburger, coffee and a muffin then turned north to Eyemouth, Pease Bay (sudden downpour as I was coming down the steep hill into Pease Bay), Dunbar, North Berwick and then home along the coast.
From Kelso to Berwick upon Tweed the route kept hopping in and out of England.
Near Dunbar Cement Works I came across an Indian-looking chap called Kishor (I think) fixing a puncture. He was riding a hugely overloaded bike (I mean hugely - he had a track pump on the back!) from London to Edinburgh. He seemed to be planning not to make it to Edinburgh that evening.
Low point was realising that the route I'd plotted accidentally included a stretch of the John Muir Way that was two miles of single track path through a field. My bike is suitable for gravel riding (apparently) but the slick tyres and close-fitting mudguards arent'. There were a depressing number of dead songbirds on the road: I don't care about dead pheasants, but tiny little songbird bodies are a shame. High points were the 100 miles downhill from Tarbrax, with a tailwind, and seeing a stoat on the road.
300km in just under 16 hours. I now need to decide whether I'm likely to get permission for a 600km before the end of the month to wrap up the SR series for the year.