The extra verse seems to be a mixture of two, as printed in Dominic Behan's book 'Ireland Sings' 1965.

The hare ran on with a wonderful view,
And swift as a rocket it crossed Waterloo,
Rose gave the first turn which is according to law,
For the second was given by Master McGrath.

McGrath paced the hare just as swift as the wind,
He was sometimes before it and sometimes behind,
Then he jumped on her back and he held up his paw,
"We've beaten the Saxons!" said Master McGrath.
Jim Mclean