The mysterious Arthur Ernest Baker

[Forfarian]

Would the registrar be present at the ceremony, to ask Arthur his details?

No, but before the ceremony they would have had to fill out a Marriage Schedule, which is the document which is signed by the couple, minister and witnesses and includes all the information later transferred by the Registrar to the Register.
 

But apart from the mother's maiden name, the London family looks very plausible.

It does indeed.

[CraigM63]

Looks like he was killed in the Boer War

http://www.roll-of-honour.com/Stirlingshire/StirlingAandHSouthAfrica.html
5th one down

According to Paul Nixon's army service number website, service number 3980 enlisted in the Argyll and Sutherland Highlanders on 7 April 1891, while service number 4543 enlisted on 22 October 1892. The A E Baker listed on the roll of honour has the service number 4080, so must have enlisted sometime between these two dates. So consistent with enlisting on or around his 18th birthday if his age on marrying in 1893 was 20.

 

[LizzieL]

I posted on a thread about service numbers

https://www.rootschat.com/forum/index.php?topic=868164.0

and ShaunJ has kindly found out some more information about him. I didn't find him on Ancestry because his initial was given as "J"

Born Highgate and enlisted 22 June 1891, Wounded 28 Nov 1899 at Modder River and died of wounds on 5 Dec 1899. So he was fatally wounded the day after his second son was born, very sad.