Political figures, family and friends came together on Friday for a service of thanksgiving for Lord and Lady Callaghan of Cardiff.
Lord and Lady Callaghan were described as devoted to each other
Tributes and readings began at the city's Llandaff Cathedral at 1430 BST.
More than 400 people attended the service to honour the former Cardiff MP and his wife, who died 11 days apart in March.
A memorial banner bearing his crest is to be hung in the cathedral.
First Minister Rhodri Morgan paid tribute to Lord Callaghan, saying the politician had always "remained true to his roots and beliefs."
Mr Morgan said the former prime minister had the "unshakeable conviction" that those less fortunate were not obliged to accept their "unequal lot in society".
Lord Brooks of Tremorfa, Lord Callaghan's agent for many years when he was an MP, praised his determination in power.
"Jim provided leadership in the constituency as well as in the national and international politics," he said.
"He saw steelworks close and manufacturing all but disappear as well as large areas of docklands lying in ruin.
"Something had to be done and something was done."
Lord Brooks also remembered the considerable efforts of Audrey who, he said, was just as well loved and respected as her husband in Cardiff.
The Bridgend and District choir led the singing of hymns which Lord Callaghan had specifically requested in a note to his family last year.
He wrote: "I would like any memorial service for me to be cheerful and joyful.... with that splendid American hymn, "Mine Eyes have seen the Glory of the Coming of the Lord. Hallelujah!" The congregation all singing. The great organ chords crashing out."
Prayers were led by members of the non-conformist community in which the Callaghans were brought up, and were marked by members the Jewish, Muslim and Roman Catholic communities.
Lord Callaghan held the four great offices of state of prime minister (1976-1979), chancellor of the exchequer, foreign secretary and home secretary.
He died on the eve of his 93rd birthday in March, 2005, His wife Audrey had died 11 days earlier. The couple were married for 67 years.
As well as being a dominant voice in national and international politics for four decades, he is also remembered for his commitment to Cardiff.
Lord Callaghan, described by Tony Blair as a "giant" of the Labour movement, was the MP for south Cardiff and Penarth for 43 years.
He was known as "Sunny Jim" to many and as a formidable opponent to some. At the time of his death, Chancellor Gordon Brown said Lord Callaghan would be mourned around the world
Lady Callaghan, the daughter of a Kent businessman, was formerly chair of the board of Great Ormond Street Hospital.
A service of thanksgiving was also held at the end of July in Westminster Abbey.