Made in 1875, they depict Royal Progresses through London. The sculptor was Joseph Kremer, a German who studied in Paris.
The monarchs concerned are:
Top: Edward VI (r1547-1553). The boy king is surrounded by courtiers and preceded by a rather fierce-looking friar on a thin nag, apparently having a confrontation with a citizen. This seems a bit odd - the religious orders had been abolished under his father and he was a staunch Protestant.
Second: Elizabeth I (r1558-1603) carried in a palanquin accompanied by a page carrying something on a cushion.
Third: Charles II (r1660-1685). Charles is announced by trumpeters and welcomed by a lady who seems very obliging. His spaniels frolic at her feet.
Bottom: Victoria (r1837-1901). The Queen rides in a carriage drawn by horses held by top-hatted grooms and escorted by cavalry officers riding very spirited horses.