body: Screenshot on the left: [*O'Sullivan & Hilliard's The Law of Contract*](https://www.amazon.co.uk/OSullivan-Hilliards-Law-Contract-Janet/dp/0198807821/ref=dp_ob_title_bk) (2018 8 ed). p. 328.  
  
  Right: Paul Davies. [*JC Smith's The Law of Contract* (2018 2 ed)](https://www.amazon.co.uk/Smiths-Law-Contract-Paul-Davies/dp/0198807813/ref=dp_ob_title_bk). p. 466.
  
  
  
  > 
  > [![enter image description here](https://i.stack.imgur.com/IIRBU.jpg)](https://i.stack.imgur.com/IIRBU.jpg)
  > 
  > 
  > 
  
  
  To what does the red underline refer? It can't be the green, as the green appears in Davies's definition of estoppel.
  
  
  
title: What "former requirement" certainly has no place in estoppel?