There is a particular pleasure in sketching British hills. They rarely announce themselves with the drama of the Alps or the Rockies. Instead, they fold into one another, soft and grey-green, often half-hidden by mist or a passing shower. To catch that sense of receding distance in your sketchbook, you need to work with thin, transparent layers of watercolour – one wash allowed to dry before the next is laid over it. This is the art of atmospheric perspective, and it is simpler than it sounds.

Start with the palest wash – and leave it alone

The farthest ridge should be almost a whisper. Mix a weak solution of a cool pigment: cobalt blue, cerulean, or ultramarine with a touch of burnt sienna to grey it down. Test the colour on a scrap of the same paper you are using – it should look like a faded memory of a hill, not a solid shape. Load a large round or flat brush (a 1-inch flat is ideal) and lay a single, even stroke across the top of the ridge. Let it fade downwards by adding a little clean water to the bottom edge, but do not go back over the wash once it starts to dry. In British damp air, this first layer may take longer than you expect. Wait until it is completely matte before moving on. If you touch it too soon, you will lift the pigment and create a patchy mess.

Mix your greens and greys for the middle distance

Once the first wash is bone dry, you can build the next ridge. This one should be slightly darker and a touch warmer, but still cool and muted. A reliable mix is ultramarine with a small amount of yellow ochre and the merest hint of alizarin crimson. This gives a natural, heathery grey-green that suits the Pennines or the Scottish Borders. Apply the wash so that its top edge sits just below the first ridge, leaving a sliver of pale paper or the first wash showing as a rim of light. That thin gap creates instant depth. Soften the bottom edge with a clean, damp brush – not soaking wet, or you will flood the wash. Remember that every layer must be transparent. Opaque pigments like cadmiums will sit on the surface and kill the illusion of distance.

Build ridges with successive transparent layers

You can repeat this process three or four times, each wash slightly stronger and warmer than the last. The trick is to keep your mixtures thin – the consistency of weak tea – and to let each layer dry fully. If you are working in a sketchbook with 300gsm cold-pressed paper, you can safely apply five or six washes without the surface breaking down. Here are a few practical rules to keep in mind:

• Wait for matte. A wash that still looks shiny will lift colour when you brush over it. Use the back of your hand to check – it should feel cool but not damp.
• Use a soft brush. A squirrel or synthetic blend mop holds water well and releases it gently. Avoid stiff bristles that scrub the paper.
• Test every mix. Keep a scrap of paper beside you. A colour that looks right in the palette often dries two shades lighter.
• Lift, don’t scrub. If you need to remove a mistake, dampen the area with clean water and blot with a tissue. Scrubbing ruins the paper’s tooth.

For the third ridge, add a little more ultramarine and a touch of burnt umber. For the fourth, introduce a hint of purple – alizarin mixed with ultramarine – to suggest distant woodland or shadowed valleys. Each layer should overlap the one behind it, but never completely cover it. Leave at least a narrow band of the previous wash visible.

Keep your foreground simple – and your shadows cool

The nearer hills and valleys can be darker and slightly warmer, but resist the urge to add too much detail. British landscape sketching benefits from restraint. A few dry-brush strokes for a stone wall, a couple of dark green dabs for a copse of trees, and a suggestion of a field boundary are enough. Save your strongest darks for the very front of the scene – perhaps a gatepost or a rocky outcrop. Even then, keep distant shadows cool and blue-violet, while foreground shadows can lean towards purple-brown. If you make the foreground too busy or too dark, the hills will flatten and the sense of depth will vanish.

Working outdoors in British light and weather

Sketching en plein air in the UK means dealing with shifting light, wind, and the occasional drizzle. A few practical habits will help. Work on a board with your sketchbook clipped down. Use a water brush or a small spill-proof water container – a jam jar is traditional but risky on a windy hillside. Limit your palette to six or seven colours: ultramarine, cerulean, burnt sienna, yellow ochre, alizarin crimson, and perhaps a sap green. That is plenty for layered washes. If the light changes, stop adding layers and make a note of the colours you see on a separate scrap of paper. You can finish the sketch at home, but try to keep the first washes fresh and spontaneous. The best distant hills are often the ones you painted quickly, before you had time to overthink them.

Above all, be patient. Layering watercolour washes is a slow, quiet conversation with the paper. Each transparent veil adds a little more distance, a little more atmosphere. On a grey afternoon in the Chilterns or a bright morning in the Lake District, that patience will reward you with hills that truly recede into the page.