First thing I did was some perspective correction using PTLens.
Used Nik Color Efex 4 - Detail extractor to bring out the detail in the building (not the sky - I like the clouds to look natural)
Cloned out the boat (then cropped because I didn't do a very good job on the cloning), selected the water and added a bit of motion blur to hide the remaining cloning imperfections.
Converted to B&W using Silver Efex (a red filter to add a bit of drama to the sky). used Topaz De Noise on the sky
Dodged the highlights in the clouds and the clock face of Big Ben. Added the border and saved.
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