From Halopedia, the Halo wiki
The Lancelot was one of the four dozen vessels present during the second Battle of Sigma Octanus IV.
It was seen by Commander Jacob Keyes charging straight into the Covenant fleet, while the other UNSC ships began to scatter. Its fate is unknown, though, given the suicidalness of this act, it may not have survived for very long after.
The ship was named after Sir Lancelot, a knight of King Arthur's Round Table.
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