Princess Diana's glitzy gown expected to fetch £100,000 at auction

Princess Diana first wore the Catherine Walker gown in 1986 during a state visit to Austria.  

She paired it with a necklace that she received from the Queen Mother.

Diana's tartan outfit will also go under the hammer in mid-June.

Diana wore the couture number during a gondola ride in Venice.

The family aboard the Royal Yacht Britannia in 1985.