Animal welfare advocate Dr Hugh Wirth has given one last demonstration of his love of all creatures by leaving a whopping $5.7 million to RSPCA Victoria, the organisation he headed, and was the public face of, for decades.

The gift, revealed in probate documents approving his will, represents the bulk of the $7 million estate left by the much-loved vet and giver of firm-but-fair pet advice on talkback radio.

Dr Hugh Wirth with his 2 border terriers in 2011. Credit:Joe Armao

Social media was swamped with outpourings of affection and sorrow for Dr Wirth, after he died at the age of 78 in February.

The RSPCA would not comment specifically on the enormous gift but Dr Liz Walker, RSPCA Victoria's chief executive, said a memorial service would be held at the organisation’s Burwood East headquarters on February 5, 2019, the first anniversary of Dr Wirth’s death.