Thames. Kent had become royalist; the marshal and Hubert de Burgh
held Sandwich, so that the long voyage up the Thames was the only way of
taking succour to Louis. Next day the old earl remained on shore, but
sent out Hubert with the fleet. The English let the French pass by,
and then, manoeuvring for the weather gage, tacked and assailed them
from behind.[1] The fight raged round the great ship of Eustace, on
which the chief French knights were embarked. Laden with stores, horses,
and a ponderous _trebuchet_, it was too low in the water to manoeuvre or
escape. Hubert easily laid his own vessel alongside it. The English, who
were better used to fighting at sea than the French, threw powdered lime
into the faces of the enemy, swept the decks with their crossbow bolts
and then boarded the ship, which was taken after a fierce fight. The
crowd of cargo boats could offer little resistance as they beat up
against the wind in their retreat to Calais; the ships containing the
soldiers were more fortunate in escaping. Eustace was beheaded, and his
head paraded on a pole through the streets of Canterbury.

[1] This successful attempt of the English fleet to manoeuvre
for the weather gage, that is to secure a position to the
windward of their opponents, is the first recorded instance of
what became the favourite tactics of British admirals. For the
legend of Eustace see _Witasse le Moine_, ed. Foerster (1891).

The battle of St. Bartholomew's Day, like that of Lincoln a triumph of
skill over numbers, proved decisive for the fortunes of Louis. The
English won absolute control of the narrow seas, and cut off from Louis
all hope of fighting his way back to France. As soon as he heard of the
defeat of Eustace, he reopened negotiations with the marshal. On the
29th there was a meeting between Louis and the Earl at the gates of
London. The regent had to check the ardour of his own partisans, and it
was only after anxious days of deliberation that the party of
moderation prevailed. On September 5 a formal conference was held on an
island of the Thames near Kingston. On the 11th a definitive treaty was
signed at the archbishop's house at Lambeth.

The Treaty of Lambeth repeated with little alteration the terms
rejected by Louis three months before. The French prince surrendered
his castles, released his partisans from their oaths to him, and
exhorted all his allies, including the King of Scots and the Prince of
Gwyn