Mosspennock was built in 1881 for James Liddell Purves, Q.C. and was designed by Charles Webb. It is unusual for the curved glass in its front bow windows. Inside is a noteworthy library initially thought to be original to the building but later determined to have been removed from another house and installed later, possisbly in the 1930s.

Purves moved to new premises c.1903 and the property became a boarding house. In 1920 it was bought by Cliveden Company. It was refurnished and renamed The Ritz, and was run in conjunction with the neighbouring Cliveden Mansions [1]. The Misses Geach ran the business. One of these,, Portia Geach, was a well known artist and feminist. Their brother, Edwin Geach, was a theatre manager and pioneer of the Australian film industry. This connection explains the number of theatre people who patronised the establishment while on tour in Melbourne.

In 1949 it was bought by the Red Cross and renamed Philadelphia Robertson House after one of its early leaders. It was later occupied by the Totally and Permanently Disabled Soldiers Association.

In the 1970s Mosspennock was bought by T & G Mutual Life Society with a view to redevelopment. The East Melbourne Group supported the move by the National Trust to have the building registered by the Historic Buildings Preservation Council.

In 1982, after lengthy negotiations, the ground floor was converted into medical suites by the architectural firm of Perrott Lyon Mathieson Pty. Ltd. The first floor was closed off to preserve the library. In 1995 the property became vacant and rumours of impending development plans were rife.

In April 2001 new owners, Thakral Holdings, applied for a permit to convert the house into four apartments and to demolish its southern wing in order to construct a sixteen storey tower. While the main house was registered with Heritage Victoria (formerly HBPC) the southern wing was excluded and was described as a 1930s extension. This was patently wrong and, along with the obvious objections to the height of the proposed building, it was the task of the East Melbourne Group to get this wing included in the registration and thereby offered some protection. The wing was in fact built by Purves as a ballroom in 1890. In February 2002 Heritage Victoria refused to grant a permit on the grounds that the tower would impact adversely both on Mosspennock itself but also on the houses in George Street. However in October it announced its decision not to include the ballroom in its register, leaving the way open for further applications. The next came a few months later, once again seeking to demolish the ballroom wing, but the height of the proposed replacement tower was reduced to eleven storeys. The EMG requested Heritage Victoria to grant them a hearing and, with an expert legal and architectural team, argued their case strenuously that the ballroom was legitimately part of the original house and should be included in the register. In 2003 Heritage Victoria overturned its previous decision and placed the whole of the land and the total curtilage of the building on the register, excluding post 1903 alterations. Development plans are still under negotiation (2008).