I have been encouraged by BillW to come out of my nest!
To reply to his last post of 31 December 2012 about travels of William Henry Halpin: I have looked more closely at the passenger lists and found that William Henry Halpin (63) and his son William Richard Halpin (15) were not actually travelling from Buenos Aires although the ship did start its voyage from there.
Mr W H Halpin b 1863, solicitor of Ford Lodge, Cavan, and his son William Richard Halpin (15) departed from Southampton on 30th March 1928 to Madeira, on the Union Castle Line ship SS Arundel Castle, final destination of the ship South Africa; They returned from Madeira to Southampton on 2nd May 1928 on board the SS Asturias (Royal Mail Steam Packet Co) via Lisbon and Vigo; the SS Asturias had set off from Buenos Aires on a regular Royal Mail Line voyage to and from South America, via France, Spain, Portugal and Madeira. It is possibly relevant that Easter Sunday in 1928 was on April 8th so I would imagine William senior was simply taking his son on holiday during the school holidays.
This is supported by finding William Henry Halpin (66) and William Richard Halpin (16) again, going to Marseilles on 5 April 1929 (on the P&O SS Mooltan to Sydney), again roughly coincident with Easter in 1929 on March 31st. William Henry Halpin also went to Marseilles on 11 February 1927 (unaccompanied) on the P&O SS Mooltan.
As I am sure has been reported before, William Henry Halpin died at Ford Lodge, Cavan on 17 April 1937, probate to his wife Caroline Isabella Emma Halpin (nee Hutton) and his son John Ralph Halpin, solicitor (left about £12,013). William Richard (Crosier) Halpin was born on 28 June 1912 in Dublin, was an accountant (Major RASC WW2, seconded to The Treasury 1942-44; company director post WW2), married Hilary Alicia Keighley-Bell, daughter of Lt-Col Henry Keighley-Bell of Hurlingham Court, Putney, in 1939 and had three children; died 1999 in Camden, London. His wife died in 2000.
Hope this solves the apparent connection with Buenos Aires - I think they were just on holiday in Madeira.