The Sheltering Tree by J.R. Lawrie

The heart of Alastair Harding’s life is duty. Becoming the first gay chief of the Metropolitan police has required certain sacrifices, but Alastair made them willingly. If his life now lacks human connections, he can’t exactly complain—and it’s a little too late for regrets.
Jay Fieldhouse knows all about sacrifice, too. Brought to London for his own safety by witness protection, Jay’s grassroots charity works day and night to save vulnerable kids from a life of crime. But getting close to other people is tough when no one really knows who you are.
When he meets Alastair one night at a charity event, Jay is intrigued by his glimpse of a gentle soul beneath the commissioner’s uniform. The two men decide to run their lonely paths side by side for a while—after all, life is short and good sex is hard to come by.
Then the shadows of the past begin to stir, and the words which go unsaid might be Jay and Alastair’s undoing.