Windsor-saippuashampoo - D R Harris London

That little aluminium tin fits right in my toiletry bag, and one bar has outlasted a month of daily use because a tiny bit goes so far in the lather. It rinses clean without leaving that squeaky-tight feeling, which I wasn't expecting from a solid shampoo.

Took it on a two-week trip and it survived the whole journey in that tin without leaking or making a mess. The lather really is voluminous—one small rub and my hair felt properly clean, and the bar barely looks used.

The aluminium tin is a clever touch—I tossed it in my carry-on for a weekend trip and it didn't leak a drop, plus one bar has lasted me over two months of daily showers. The lather is genuinely rich and rinses out clean without that squeaky-tight feeling.