IRC Boken Plus gravel tyre 650B
IRC's Boken Plus multi-surface tyre rolls well on tarmac and is surprisingly capable on much rougher terrain too.
This is a semi-slick tyre with a solid centre tread that gets increasingly open the further you move from the centre line. There's a herringbone section on either side of the middle, and then two sections of blocks on the shoulder.
The idea is that the middle section rolls well on smooth surfaces, and then the more open tread comes into play when the bike is cornering, and when the surface is uneven and the tyre deforms over obstacles. It's built around a tubeless-ready carcass.
Reviewer Dave Atkinson used these tyres on a variety of rides and was impressed with the level of grip they offer. Tarmac sections were a breeze: the unbroken centre strip makes them nice and quiet on the roads, and they're also stable and predictable through the turns.
More impressively, the Boken Plus coped with loads of varied terrain with very little fuss. They're great on graded gravel, but they're also really good on steeper, rockier stuff. With the pressure reasonably low, once they start to deform over the surface of the trail they really bite, offering up much more grip than you'd imagine the design would provide.