My entry updated.
This time TS-E 25 plus an ND10.
Hmmm... should I explain that for the benefit of the people who are new to the technique?
I have used the tilt in a 24mm tilt and shift lens. The lens is tilted towards the ground to move the focal plane from being vertical to near horizontal. This gives me the opportunity to get the groves in the concrete in focus at the same time as getting the detail in the cliff sharp.
Screwed on the front of the lens is an ND10 filter. This gives 10 stops of darkness. On this bright, sunny day, I was able to wind all the way out to a 30 second exposure, which gives the glassy effect on the pond, adds a dynamic effect to the sky as the clouds move and reduces the detail of the people having a picnic - they are still there but they don't attract so much attention.
Andrew