First the bridesmaid, then the bride

Another example of why it pays to advertise, ie publish your research, and the gaps.
In my inbox today arrived a certificate and a note  saying "I think I've found the first wife of the Rev. Robert TURNBULL for you".
Sure enough!!
The Robert on the cert. was shown as a schoolmaster, son of a carpenter Robert.
So far so good.
Even better, one of the witnesses was a Dav[id] STEVENSON.
The Revd Robert's son Robert, later Sir Robert of the LNWR, is to be found in the 1871  census as a visitor in the household of a David STEVENSON, a railway manager, born Islington, MDX.

And just to make even more certain, another of the witnesses was one Louisa Philippine MAES.

Timeline:
Jan 1843 Robert marries Mary Ann LIVOCK, daughter of John LIVOCK, Coal Merchant.
Nov 1844 Robert marries, as a widower, Louisa Philippine MAES.

Now to find Mary Ann's death.
One possibility in Pancras looks a few short weeks prior to Robert's marriage to Louisa!!
There are others to investigate.

My benefactor was interested in the LIVOCK family because of John William LIVOCK the architect who had designed railway stations.
He had added that Mary Ann's sister Eliza married David STEVENSON, the witness, and with whom (Sir) Robert was in 1871.
This branch of the TURNBULL family does seem to attract railway connections.

Now I'm on the hunt to identify Mary Ann and Eliza's mother as she appears to have been born in Cumberland.
This family may well do a full research circle, Cumberland to St Pancras and back to Cumberland.