Janet Marion Clarke was born on 4 June 1851 at Doogallook Station on the Goulburn River, Victoria, the eldest of nine children of the affluent landowner Peter Snodgrass and his wife Charlotte.

In 1869 Janet became governess to the four children of the Hon. William Clarke the landowner and stud breeder. William’s wife Mary died in 1871 and Janet and William were married in 1873, when Janet was 21 and her new husband 41. William and Janet went on to have four sons and four daughters together with one son and one daughter dying young.

In 1874 on the death of his father William inherited properties worth about £1,500.00 which enabled him to become the largest landowner in the colony. That same year William began to build the mansion Rupertswood in Sunbury. As the wife of a prominent man and the chatelaine of a fine mansion, as well as looking after a large family, Janet also took part in an active public life.

Her grandson Michael has noted that his grandmother was “conscious of her deficiencies. She covered up her ignorance by being a good listener. She concealed her lack of social know-how by being a thoughtful hostess and a cautious guest. She was deferential to her elders and betters, kind to nervous young ladies and considerate to servants”.

In 1881 William engaged the builder David Mitchell, father of Dame Nellie Melba, to build the three fine, three storey terrace houses at 92 - 96 Hotham Street and named them Janet Terrace after his wife. The Clarkes never lived there however, retaining their residency at Rupertswood. 

In 1882 according to legend, but contested by some, it was at Rupertswood that Janet famously presented the Ashes urn to Ivo Bligh, captain of the English Cricket team, which has since become the trophy awarded to the winner of the Test Cricket Series between England and Australia.

In 1882 William was made Australia's first baronet in recognition of his philanthropy. 1888 saw Sir William and Lady Janet Clarke and their children move into their fabulous newly built twenty-eight bedroom townhouse Cliveden. Standing on the corner of Clarendon Street and Wellington Parade the Italian Renaissance style residence enjoyed views over the Fitzroy Gardens and the MCG. 

As Melbourne's largest house at the time Cliveden became the centre of the elite social world and the Clarke’s were famous for their lavish hospitality at garden parties, luncheons, dinners and balls. Punch Magazine suggested that “most of the big charitable works which had been carried through to successful issue in Melbourne...had their origins in Lady Clarke's ballroom.” 

Janet led society in Victoria for 30 years and she was a familiar face at race meetings and all the major yearly social events. She was entertained in England over the years as one of the best known Australian women of the time. 

Janet believed that her wealth brought her obligation to those in need and she became an enthusiastic philanthropic supporter of educational, cultural and political movements. She was very actively involved in a large number of hospital committees and charitable societies.   In the depressed 1890s she opened up the kitchens of Cliveden to feed hungry Richmond and Collingwood families at her own expense and cases of personal hardship were helped with generosity and kindness.

Janet made huge contributions to education. She helped in the establishment of the College of Domestic Economy (which became the Emily McPherson College) and the Melbourne Church of England Girls' Grammar School. The Janet Clarke Hall for women university students at Trinity College was built in 1889 with her generous donation. In 1904 she was president of the University Funds Appeal, raising £12,000. 

She promoted domesticity as women's natural duty rather than suffrage. She did believe though that women's maternal and domestic influence was needed beyond the family home. Once women had been given the vote she became president of the Australian Women’s National League which raised the political awareness of Melbourne women, especially those within her social milieu.

Upon the death of William in 1897 she took the title of Janet, Lady Clarke and continued her life at Cliveden until her death on 28 April 1909. Her funeral was held at St Paul’s Cathedral. She was mourned by many who had either known her personally or who had been helped by her generosity. On the occasion of her death the Leader said that “she had stood at the head and front of almost every philanthropic movement.