It remained impossible, in fact, until someone made it in 1995.

For decades the particle remained impossible to pin down and the hunt for it became the focus for the LHC.

Gilbertus knew he had run out of acceptable excuses to grant his mentor such a wish, but it remained impossible at present.

So it has remained impossible (if I may anticipate a little) to ascertain what was conveyed in this curious message or commission.

Mr Joyce said regular UK and US services remained impossible while both regions struggled to contain the virus and there was no vaccine readily available.