When police tried to follow they were blocked by members of the church.
You have to remember this is Northern Ireland before you move next to a church and start a whole new career as a criminal mastermind.
The last instance I could find of someone claiming the medieval right of sanctuary was the case of Viraj Mendes who took sanctuary in a Manchester church about twenty years ago, to avoid being deported back to Sri Lanka. He had a rather more morally defensible position. He was afraid he’d be killed in Sri Lanka. He wasn’t just dodging a speeding ticket.
In any case, sanctuary didn’t even work for him in the end.
The stand off lasted 760 days before police battered down the doors with sledgehammers and removed him.(From the BBC)
Disappointingly for that new master-criminal career, the BBC said that
the right of sanctuary had no legal force for centuries
(Try telling that to the congregation of the Free Presbyterian Church in County Tyrone.)