'shooting' the bridge: passing through the arches in a boat.
Queen Henrietta was the queen of Charles I. of England. After the Civil War she withdrew to France, where she died in 1669.
Rubens: a very celebrated Flemish painter, born in 1577, died at Antwerp in 1640.
Sir Thomas Wyatt headed a rebellion in Kent, which was provoked by Mary's marriage with Philip of Spain and the restoration of Roman Catholicism. He was about to cross London Bridge, but finding this impossible crossed the Thames at Kingston. The rising was a failure, and Wyatt was executed, 1554.
Sir William Wallace: a brave Scotch gentleman who led the Scotch against Edward I., who was trying to deprive Scotland of its independence. Wallace was finally taken and executed as a traitor at Tyburn, 1305.
Jack Cade headed a rebellion in Kent in 1450 through dissatisfaction with the government of Henry VI.: 30,000 rebels gathered on Blackheath, but the movement ended in failure and Cade was slain.
Sir Thomas More: the good and learned chancellor of Henry VIII., and author of a famous book called 'Utopia.' He was executed as a traitor in 1535.
St. Thomas-on-the-Bridge: that is, Thomas Becket, to whom the bridge was dedicated.
pageant: a splendid show or procession.
ex-apprentice: one who has been once an apprentice.