I'm asking about the red underline. John D McCamus. The Law of Contracts (2012 2 ed). p. 229
Mountford & Anor v Scott  EWCA Civ 10 (17 October 1974)
The third ground of attack on the validity of the option agreement was that the consideration for the grant of the option, stated and paid, namely £1, was a sum which the law would not regard as valuable consideration: therefore there was no consideration in the eye of the law to support the obligation on Mr Scott not to withdraw his offer for six months. This I found a startling proposition. The industry of Mr Narayan has not been able to find any support for it in English authority; and his reliance on a Canadian case of Gilchrist v. Sedley, which is reported in (1967) 66 Dominion Law Reports, Second Series, page 24, was based on a misreading, in my view, of the decision in that case, which appears to me to suggest only that possible future obligations which could be avoided by payment of £1 were illusory as consideration.
Anson's Law of Contract (2016 30 ed). p. 104
(f) CONSIDERATION NEED NOT BE ADEQUATE
Thus specific performance was ordered of an option to purchase a house for £10,000 even though the consideration for the grant of the option was the nominal sum of £1.53
53 Mountford v Scott  Ch 258 (Brightman J). But note that, in contrast to Brightman J, the Court of Appeal in that case regarded the option as having been exercised so that the specific performance related to the contract of sale for £10,000 not the option contract for which the consideration was nominal.