My entry had a typo, should have said 1911 as Heywood has pointed out. I have amended it.
If William Johnson was the vermin catcher, he died in 1898, so Mary would have been a widow as 1901 census suggests. William's headstone at Biddenham makes no reference to Mary, just his 2 earlier spouses. If he indeed had married Mary Bowler (nee Garratt) I suspect the omission could have been intentional.
I have found them in 1891 census, he widower living in Biddenham, widower and she a widow, laundress, living St Paul's Bedford.
As amondg and johnP-bedford suggest it does look like a Registry Office marriage.
Thank you, O.