at the last moment , gruffudd swerved to the left , the norman jabbed ineffectually at the air where the others body should have been , the welshman plunged his own sword into the unprotected chest of the knights horse and ripped it out viciously and then , as the animal shrieked and sank to its knees , he freed his foot from the stirrup and kicked the normans head with all his might and momentum .