Aristotle believed in a fixed earth that was also eternal. When Aristotle was Christianized by Aquinas in the thirteenth century, Aquinas deemphasized the eternality of the earth as inconsistent with Genesis which taught that the earth had a beginning, but had no problem retaining the fixed earth idea. After all, there were Scriptures that seemed to support that notion:
Tremble before him, all the earth; yes, the world is established; it shall never be moved. (1 Chronicles 16:30)
Yes, the world is established; it shall never be moved. (Psalm 93:1)
He set the earth on its foundation, so that it should never be moved. (Psalm 104:5)
For the pillars of the earth are the Lord's, and on them he has set the world. (1 Samuel 2:8)
Lennox notes that the Bible also seems to indicate that the sun moved around the earth:
In them he has sent a tent for the sun, which comes out like a bridegroom leaving his chamber, and, like a strong man, runs its course with joy. Its rising is from the end of the heavens, and its circuit to the end of them, and there is nothing hidden from its heat. (Psalm 19:4-6)
The sun rises and the sun goes down, and hastens to the place where it rises. (Ecclesiastes 1:5)
So when Copernicus proposed a heliocentric view of the cosmos this was startling and called into question by both Protestants and Catholics. Martin Luther railed against the idea in his Table Talk. Calvin, likewise, rejected the notion.
About 80 years later, Galileo published Dialogue Concerning the Two Chief World Systems, a work validating the heliocentric theory and earning the ire of both Aristotelian philosphers and Christians as well as becoming the prototype of the church-is-anti-science nonsense. Though the "mistreatment" of Galileo is often overhyped (his imprisonment was in the estates of his wealthy supporters and he was never tortured), nevertheless the case does represent a black eye in the Science vs Religion smackdown, especially seeing as how none of us, even committed Christians, remain these days as fixed-earthers. Lennox's closing question is to ask Christians to consider that if we have abdicated our fixed-earth belief because of compromise and thereby made Scripture subservient to science?
While I understand his point here, and anecdotes are fun, they don't exactly make for good policy. Say you know someone who defended a home robbery attempt with their firearm, then you are all like "rah rah guns save lives." Or say you know someone whose five-year old found the family gun and shot his sister, and then you are all like "guns are evil!" Neither position is really validated by your test case.
It strikes me as the same in this instance. Sure, the Church gave up on the fixed-earthedness of an overly literal reading of obviously poetic passages, but we are asked to give up something more by accepting an old earth governed by Darwinian forces. I mean, we have all been moving-earthers our whole lives, but I still talk about the sun coming up and no ardent scientist has ever said, "Hey you blankety-blank, don't you know that the sun is fixed and we are spinning around it at 67,000 miles per hour in an elliptical pattern that means it is dark when you get out of work in the winter and some places in Alaska don't see the sun for a whole month? What are you, anti-science?"
In other words, science these days isn't telling us, as Galileo did, that we simply misunderstand something about the way God created the world. Science today is telling us that there is no God and something about primordial ooze and that if you believe in God you are just as stupid as someone believing in a flying spaghetti monster (which would be dope, if it was real). The stakes are a bit different, as what is being called into question is more severe.
I know Lennox knows this, and perhaps I am being uncharitable here, but anecdotes frustrate me. I understand his broader point--the Church should be willing to change when it is definitively proven to be wrong in its understanding of something and has done so in the past--and I will withhold further judgment until I know what Lennox suggests we replace a straightforward understanding of Genesis with, but if you are ever writing a book, please don't start with an interesting story that is at best tangentially related to the one you are attempting to tell. I read this book one time that started that way, and it didn't turn out well.