Fredericks was formerly a British national

In partnership with her 2002 Blenheim winner Headley Britannia, the 40-year-old Australian put in a masterly dressage display.

Germany's World Games team gold medallist Bettina Hoy, on Peaceful Warrior, is in second by 1.5 penalties.

And Hoy's Australian husband Andrew finished the day in third on the first of his two rides, Mr Pracatan.

Fredericks, who is based near Devizes, switched from British to Australian nationality when she married Clayton Fredericks, team bronze medallist at the World Games.

Her aim at Burghley is to make up for the disappointment of being dropped from the Australian team at the World Games in Aachen and she is confident going into the cross-country.

Fredericks said: "Headley Britannia is very bold across country, so I shall be bold, as the course walks that way.

"I've just got to keep my head on straight. It's a difficult course, particularly the railway fence number nine. Every fence feels like a drop because the mare is so small and jumps so high."