What &quot;former requirement&quot; certainly has no place in estoppel?
<p>Screenshot on the left: <a href="https://www.amazon.co.uk/OSullivan-Hilliards-Law-Contract-Janet/dp/0198807821/ref=dp_ob_title_bk" rel="nofollow noreferrer"><em>O'Sullivan &amp; Hilliard's The Law of Contract</em></a> (2018 8 ed). p. 328.<br>
Right: Paul Davies. <a href="https://www.amazon.co.uk/Smiths-Law-Contract-Paul-Davies/dp/0198807813/ref=dp_ob_title_bk" rel="nofollow noreferrer"><em>JC Smith's The Law of Contract</em> (2018 2 ed)</a>. p. 466.</p>

<blockquote>
  <p><a href="https://i.stack.imgur.com/IIRBU.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IIRBU.jpg" alt="enter image description here"></a></p>
</blockquote>

<p>To what does the red underline refer? It can't be the green, as the green appears in Davies's definition of estoppel.</p>

<p>'The former' means the first part of the green:</p>

<blockquote>
  <p><strong>the mistake ‘must be one calculated to
  benefit’ the non-mistaken party</strong> <s>or to be detrimental to the mistaken party</s></p>
</blockquote>

<p>Estoppel works to prevent harm to the misled, not to prevent benefit to the misleader.</p>

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