Um, I know I left school a long time ago - over 45 years - but I think that your KW to HP conversion may be a little out. 3,300 KW is about 4,425 HP. The most powerful locomotives were - as has been stated - the Princess Coronations. On test one managed a drawbar pull of 3,333 HP. That was with two firemen continuously shovelling coal onto that enormous 50 square foot grate (imagine a square 7'X7'). I doubt that an A4 could knock out much more than about 2,300HP at the drawbar.
Bear in mind that power doesn't necessarily equal speed or speed necessarily equal power. The analogy might be an elephant and a cheetah. Which one is strongest, which one is fastest?
Of course Barlow Boy you are correct. And 1 hp is still 746 Watts! I was probably thinking of the Princess Coronation Class when I noted that in the earlier days of diesel, steam was still king, and that was 3300 hp at the bar of a Princess Coronation. Gresley noted that what could be done with diesel could be done with steam, and that is why he continued with it for so long. Next time engage brain before writing.
Speed or strength? It was probably that the King Class could pull the heaviest loads. I heard that one GWR director having been asked to explain why his main line steam loco was costing more than an A4 to produce responded, 'It can pull two of those things backwards!' The King Class were powerful beasts, but I think you are right the Big Lizzies probably pipped them.
My uncle Percy was on the Big Lizzies on the West Coast Mainline route. He loved them, but noted that they had been developed to replace the earlier Princess class locos. Why? The Princess class were crap firers. Poor steamers. No wonder the firebox area was so large on a Princess Coronation Class. The LMS had decided that on the replacement for the Princess class steaming would not be a problem.
Yes, interesting past........Herbert Spencer (mothers side), Bill Mayes - engine drivers on LNER/BR - I have my grandfather Mayes BR 45 year long service award, a Smiths gold watch engraved, Ted Mayes - senior instructor with LNER/BR - later to be involved much with HS4000 Kestrel tests - uncles Donald, Keith, Malcolm Spencer (mothers side) - firemen on LNER/BR, uncle Percy - main line West Coast services on LMS/BR from Euston to Glasgow (I think). Every Saturday afternoon endless discussions of the railway rule book, and arguments about who was the best when Percy visited nearly drove my grandmother beserk.
How I did not end up on the railways? I will never know! Probably I lost it when steam left. Had Flying Scotsman (without crew) all to myself on Shirebrook station in about '68. After a civic function on the platform (I could not get anywhere near her so looked on from the bridge as she pulled away), she had to reverse back due to a points failure on the Mansfield loop. Great memories. Just me alone with the loco. I always remember touching her name plate. The smell of a steamer still attracts me even today. Wonderful smell. Steam......it is in my blood!