In 1888 John Grimwood appears to have given evidence at the Old Bailey trial of Leon Serne & John Henry Goldfinch, both charged with arson. Serne was found guilty and sentenced to 2 years penal servitude, Goldfinch was found not guilty.
Below is Grimwoods evidence taken from the court transcript (OldBailey on line). This provides you with his Divisional no E397.
John Grimwood (Policeman E 397). On 18th September, about 1. 35 a.m., I was on duty in the Strand, and saw smoke issuing from the top window of 274, I came from the east, from Temple Bar; I ran for a fire-escape and called the firemen—the escape came about three minutes afterwards—I assisted the constable in trying to force the doors open, and rescue the inmates—I went to 275, and had to come back—I then went to 277, where Mrs. Serné was rescued.
Alex