What built this nest?

What built this nest?

Observation - What built this nest? - UK and Ireland. Description: A nest made of folded leaves, glued (?) together, or perhaps 'stitched' together. This was in amongst the nettles alongside a chalky track - part of the South Downs Way - but at a low-level, where the Way crosses the River Arun.

A nest made of folded leaves, glued (?) together, or perhaps 'stitched' together. This was in amongst the nettles alongside a chalky track - part of the South Downs Way - but at a low-level, where the Way crosses the River Arun.