I remember reading this somewhere, and I'll update this post if I find the book, but aren't you supposed to cite primary law like cases and legislation first? Even if written by judges or jurisprudes, law textbooks aren't authoritative. Is the author wrong to cite Clerk & Lindsell on Torts on the general four elements of negligence? The library is closed, but I'm certain there must be some leading UKHL or UKSC that dictated the general four elements of negligence.
To establish liability in negligence, a claimant must prove the existence of a duty of care, the breach of that duty, causation and damages. These elements are found in virtually every case and treatise on tort, so you can provide support for this proposition by citing to Clerk & Lindsell on Torts, for example, or a seminal case on each point (for example, *The Wagon Mound (No 2)*8 for causation).
8 Overseas Tankship (UK) Ltd v Miller Steamship Co Pty (The Wagon Mound (No 2))  1 AC 617.
Stacie Strong. BA English literature (UC Davis 1986), MPW (USC 1990), JD (Duke 1994), PhD Law (Cambridge 2002), DPhil (Oxford 2003). How to Write Law Essays & Exams 5th Edition (2018). p 73.