It is the most signifiant appointment of the mini Cabinet reshuffle - Wallace was a senior figure in the UK's response to the Ukraine war and Shapps will now have a greater presence on the international stage compared to any of his previous roles (of which there have been five in the past 12 months alone).
Shapps' elevation has led to increased scrutiny on his past - including the previous controversy surrounding his alter egos Michael Green, Corinne Stockheath and Sebastian Fox.
Read more: Grant Shapps appointed UK's new defence secretary (Sky News)
The web guru
In 2012, photos were leaked of Shapps at a 2004 conference using the "business name" Michael Green, a supposed web guru linked to the How To Corp business he started with his wife.
The How To Corp was a web publishing business that told online users they could "make $20,000 in 20 days guaranteed or your money back" if they invested $200 in software. And while Shapps acknowledged that he had started the business and worked as "web guru" Michael Green, he indicated he had not done so since becoming an elected member of Parliament in 2005.
Shapps told Sky News in 2012: "Before I went into parliament I used to write business publications, and like many authors wrote under a business name. I was always very open about it and I actually went to one conference, where that picture was from, it was sort of open fact. It was in my biography, it was in the conference programme.
"I have seen some extraordinary headlines though, things about living double lives as though I was François Mitterrand with his second family and things.
"My wife and I set up the business, we were always very open about it and had a business author's name as many authors do. It was all a long time ago. I've not been involved for a long time."
'I don't have a second job'
As recently as 2015, Shapps had denied having a second job during his tenure in Parliament, telling LBC in an interview: "I thought the discussion here was second jobs whilst people are MPs. To be absolutely clear. I don’t have a second job. And I have never had a second job whilst I being an MP. End of story.”
Indeed, he continued to deny that he had worked under the name Michael Green - or other business aliases Corinne Stockheath and Sebastian Fox - after becoming an MP.
That was until The Guardian in 2015 located a recording in 2006 - the year after he became an MP - of him telling listeners they could make a 'ton of cash by Christmas' using his products.
In a subsequent statement, a spokesman for the Conservative party said: “Like many authors and journalists, Grant wrote with a pen name. This was completely transparent: his full name and biographical details were permanently published on the company’s main website.
"Given that this was a decade ago, and was mentioned during the cut and thrust of an interview, he referenced that his writing career had ended when he became an MP: in fact it ended shortly afterwards.”
It's a controversy that Shapps has been unable to shake off.
In January this year, Dawn Butler referenced Shapps' alter egos in a debate about party funding.
Dawn Butler asks Grant Shapps how much Michael Green, Corinne Stockheath & Sebastian Fox have received in payment. pic.twitter.com/g0r3Trt6kF
— Haggis_UK 🇬🇧 🇪🇺 (@Haggis_UK) January 16, 2023
And his appointment today sparked more mentions of his alter egos.
A man who made his fortune selling get rich quick schemes on the internet under a variety of false identities- and lied about it *after* becoming an MP - is now in charge of the nation's defence.
— James O'Brien (@mrjamesob) August 31, 2023
Grant Shapps to job-share defence secretary post with Michael Green, Corinne Stockheath and Sebastian Foxhttps://t.co/4R9loFfFjY
— Simon Hattenstone (@shattenstone) August 31, 2023
The new Defence Secretary is #GrantShapps. Some Tory backbenchers complain that he has no military experience. Not to worry. Perhaps Michael Green, Corinne Stockheath and Sebastian Fox have served in the forces.
— John Williams (@legalolder) August 31, 2023
New Defence Secretary to be job-share:
Monday: Grant Shapps
Tuesday: Sebastian Fax
Wednesday: Michael Green
Thursday: Corinne Stockheath
Friday: day off.
— Prof Colin Talbot (@colinrtalbot) August 31, 2023
Man who used the pseudonym Michael Green to earn a fortune selling get-rich-quick dreams(including when he was first an MP) is the UK’s new Defence Secretary.
Move along please, nothing to see with a downgrade to Grant Shapps.
— Kevin Maguire (@Kevin_Maguire) August 31, 2023