Overtrousers are an easy thing to skip until the first properly wet commute of the year, at which point a jacket alone isn't enough. Endura's Hummvee Transit trouser is a dedicated waterproof overtrouser built for exactly that job, using a lightweight two-layer waterproof fabric with fully sealed seams rather than a basic showerproof coating.
They're designed to pull on over whatever you're already wearing, with an elasticated waist and stretch shock cord for a secure fit and wide, Velcro-adjustable leg openings that go on over shoes without needing to remove them. Endura's commuting range is built around durability and packability rather than racing weight, and the Hummvee Transit reflects that: a durable seat panel takes the wear from a saddle, and a PFC-free water-repellent finish means the fabric surface sheds rain rather than soaking it up.
For anyone riding an e-bike through a UK winter in normal work or casual clothes, a proper waterproof overtrouser is the difference between arriving dry and arriving having sat in wet trousers for the whole commute.