Mr Groser was ambassador for three and half years in the mid-nineties and developed a passion for the country, its culture and people, even converting to Islam while there.
But during his term there he was at times summoned by Indonesia's Foreign Ministry to answer questions about the Indonesian flag being burned during New Zealand protests about Indonesia's presence in East Timor.
He even once sheltered five young Timorese at his embassy before they were granted political asylum in Portugal.
He left the country in 1997 just as what began as a run on the Thai baht developed into the Asian economic crisis and in turn brought down the authoritarian Suharto regime.
"What has happened since then is Indonesia is now a fully fledged democracy and that is something to celebrate", said Mr Groser.
While Indonesia has since made huge progress in addressing poverty and human rights issues, relations with New Zealand were chilled until recent times owing to the Labour Government's refusal to recognise Indonesia's claim over West Papua.
However, things have warmed up again since Mr Key's Government chose to recognise Indonesia's "territorial integrity".
That makes for a more successful political relationship from which everything else follows.
"That's why the Prime Minister is leading the delegation," said Mr Groser.
"It's a statement from us, a tiny country, that we treat Indonesia seriously and we want to build that relationship."
The visit is part of the Government's "frenetic activity" to lift exports via 28 minister-led trade missions around the world.
While China appears to be the obvious target of Foreign Minister Murray McCully's controversial refocusing of his ministry away from Europe towards Asia, the Government regards Southeast Asia as just as important.
The Asean Australia New Zealand Trade Area signed in 2009 gives New Zealand and Australia a unique opportunity with Southeast Asia and came into force in Indonesia in January. But without further effort, says Mr Groser, it's "just a piece of paper".
Of the 10 Asean members, Indonesia accounts for 45 per cent of the bloc's GDP.
"Indonesia is the game in Southeast Asia."
Mr Groser says the geological forces that make both New Zealand and Indonesia perilous places to live also offer particularly interesting potential for trade in services around geothermal energy.
New Zealand has been involved in Indonesia's geothermal sector since its beginnings in the early 1970s and has trained many of its geothermal engineers.
So far, New Zealand's input has been largely through training and consultancy work but the presence of construction industry leaders on next week's trip as well as Mighty River Power demonstrates an industry-wide push to step up involvement.
Mr Key also has some political skin in the game - Mighty River is the first of the four state-owned energy companies to be partially privatised under the "mixed ownership model" that will allow the companies to expand theiroverseas businesses.
Success for Mighty River in Indonesia would serve as some "proof of the pudding" which Mr Key says New Zealanders who have doubts about the mixed ownership model will see once the programme goes ahead.
