Sometimes, when the light is dull and the contrasts are subtle, as was the case yesterday, monochrome does it best.
Working mainly with colour, as most of us do nowadays, it's easy to forget the importance of pure tone. It used to be what photography was all about. A wise photographer once said to me that no-one should be allowed to use colour until they have mastered black and white. You might say it is the equivalent of drawing in relation to painting -- splashing colours about is fun, but leads nowhere very interesting without the underlying disciplines of line, shape, volume, tone, and balance.