The Tippett - but that was a long time ago when even though I was already only too well aware that I was almost the very opposite of a pianist I nevertheless felt that I ought at least to make some effort (or was it pretence?) at being one; a good choice under those circumstances, really, because, for the most part, Tippett had not much more of a clue about writing effectively for the piano than I did about playing it in those days, for all that his concerto is itself quite attractive (and actually sounds a whole lot more like reasonably decent piano writing than is actually the case most of the time). His best solo piano work, by the way, is his Third Sonata, I think.
Best,
Alistair