He had a plan to project the names of veterans on to the hall of memory at nighttime, a proposal that even then sparked questions about turning the memorial into a theme park.

The one-time doctor, former defence minister, Liberal leader and ambassador to Europe was appointed by Labor's Warren Snowdon to the job that had been held for 16 years by Major-General Steve Gower.

Dr Nelson's predecessor describes him as a man who brought showmanship, contacts, energy and romanticism to the role.

Preparations were underway to mark 100 years since World War 1, an event that was set to benefit from Dr Nelson's "high-level political contacts, an ease and readiness to appear at major public events, with a talent for showmanship, retail salesmanship and public speaking".

"It soon became apparent to all that the frequent conduct of high-visibility public commemorative events would have a high priority," Major-General Gower says, writing in his history of the memorial, published this year.

He identifies a new tone that Dr Nelson brought to speeches - "passionate, sentimental and sometimes romantic language" that had been out of favour since Vietnam.

Dr Nelson has courted controversy for his willingness to accept military sponsorship of the memorial and for accepting more than $500,000 in donations from Chinese-Australian businessman Chau Chak Wang - a contact whom Dr Nelson approached for donations early in 2013.

The Medical Association for the Prevention of War says the memorial should not accept donations from the world's big weapons manufacturers and military suppliers, and it criticises efforts under Dr Nelson to make visits fun, through dress-ups for children and interactive displays.

Former director Brendan Kelson has been scathing about donations from weapons manufacturers, telling a parliamentary inquiry last year that it showed "an institutional loss of moral compass", was at odds with everything the memorial stood for, and was "an affront to all who served and died".

Mr Kelson is among a long list of people to criticise Dr Nelson's flagship achievement - the securing of $500 million for a big expansion and partial rebuild of the memorial, creating space for exhibitions of helicopters and fighter jets.

Major-General Gower is more guarded, but says in his book that the excavations under and around the main building are potentially "very tricky".

Speaking on Thursday, Major-General Gower said he was sorry to see Dr Nelson leave. He had made a great success of the World War One commemorations and "done a very good job in public programs".

"It's very disappointing he's not staying to see it through," Major-General Gower said. "No project is plain sailing. I'm really surprised he's leaving because he's got in front of him a really challenging project."

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Dr Nelson took over the memorial soon after it had hit a budget crisis, under a government efficiency dividend, according to Major-General Gower's history. It was facing staff cuts and gallery closures when prime minister Julia Gillard stepped in with an $8.3 million budget increase.

Dr Nelson had embarked on "wholesale rearrangement" as soon as he had taken the job in 2012. He had made a controversial change to eligibility for inclusion in the roll of honour, directed a refit of the Terrace cafe, expanded the closing ceremony and gave Afghanistan an exhibition of its own.

He had political leaders hold a joint wreath-laying ceremony to mark parliamentary sittings, and he invited them to take part in "what he regards as a transformative, spiritual and emotional experience" of kneeling to clean the Tomb of the Unknown Soldier.