What's the name for the fibrous mat that goes between the house wall & a garden wall to allow for expansion/contraction?

[BoiledFinger]

I need to get a wall repaired which doesn't have this stuff & I want to put it in but I don't know what it's called. Any ideas?

Expansion joint filler
www.travisperkins.co.uk/expansion-jointing/fillcrete-brickfill-expansion-joint-roll-10mm-x-100mm-x-10m/p/837980

Genius! Thank you. For anyone else reading this, do you think the foam stuff will last as well as the fibrous stuff? I imagine the foam would decay in say 10yrs?

I think it's intended to be protected with a bead of mastic at the surface. Manufacturer website states that fibre board no longer approved for brick applications. I think because brickwork expands/contracts more than concrete.
data sheet

there would be no point selling a product than disintegrated in 10 years.