I have a similar situation. One of my Devon ancestors is shown as married in 1871, but no sign of husband.

They are together in 1881, having moved to London.

First child born 1872. But on the birth cert, he is 6 months old when the birth is registered.

Several other children are born, all registered with the 'married' name.

When the mother dies in 1887, she is registered under the 'married' name.

The father marries shortly after her death, and declares he is a widower.

I am darned if I can find a first marriage, though.

I suspect the delay in registering the first son was caused by a will they/won't they marry situation.