A leading police officer who was part of the investigation into the fire branded the diabolical actions of the Philpotts as "stupid" and "shameful".
Assistant Chief Constable Steve Cotterill, of Derbyshire Police, said that not only was the setting of fire itself an "evil" act, but Mick Philpott's reaction to it nothing more than a "sham".
He met the couple on 16 May as they held a press conference, five days after the fatal fire in which the youngsters died. Mairead Philpott was mother to all six, while Mick Philpott was the father of five but had raised Duwayne as his own son.
Mr Cotterill described the behaviour of Philpott that day as the most astonishing he had seen in three decades of policing.
"After 30 years of doing what I do I have never seen anybody having suffered that magnitude of loss deal with it in the manner in which he dealt with it," he said.
"I would have expected him to be completely and utterly destroyed, and if push came to shove not able to present himself at the press conference."
Question marks around Philpott and his wife's involvement in the fatal fire had already been raised in the minds of police by this time, and witnessing Philpott's performance at the press conference - in which he dabbed at his eyes as with a tissue and buried his face in his hands, but notably no tears fell - was like watching an actor playing a part.
Mr Cotterill sat beside the couple during the meeting with the media, which had been Philpott's idea because he claimed he wanted to thank the public for the efforts they made in trying to save the children.
Mr Cotterill said: "What's going through my head at that point is that I'm torn between trying to care for the parents of six dead children and that, professionally, this is a dilemma.
"I've got that at the back of my mind, I've got managing the press conference, which by any stretch of the imagination is a pretty big press conference, but also looking at what I can only describe as a shameful performance from Mick Philpott - and I stress Mick Philpott because Mairead had virtually buried herself in Mick Philpott - and this dabbing of his eyes with the tissue.
"It was a sham, in my view."
Mr Cotterill said he had decided police should be involved because at that point his suspicions were just that, and officers had no concrete evidence.
He was also aware that media interest would be great and that Philpott was a "loose cannon" whose behaviour, if unmanaged, could change the course of the investigation.
He met the couple in a private room before the press conference to introduce himself and to explain what was going to happen.
What he witnessed from Philpott during that meeting was a total shock, he said.
"He entered the room in quite a jovial manner as though it was a bit like an excited child, really inappropriate in my view," Mr Cotterill said.
"He was the father of five children, in essence six children, who had died in his house. I didn't see it as anything to be excited about.
"If anything he should be rather fearful of the experience and wary of it.
"I didn't see a great deal of emotion and upset."
Philpott continued his sham after the meeting with the media - which Mr Cotterill said he thought Philpott might have been looking forward to until he saw the number of reporters and camera crews present - and carried out what seemed to be a fake collapse.
Mr Cotterill found him face down on the floor in a corridor.
"It was a childlike performance, that's the only way I can describe it," he said.
"My initial thought was: 'what on earth are you doing down there?' because it was plain to me that this was not somebody who was distraught and unable to stand.
"He was being tended to by a couple of officers that were there, within a matter of 10 to 20 seconds he was back on his feet and back to his normal self.
"Again, it was just part and parcel of a continued performance, and not a good one at that."
Detectives had started to suspect the Philpotts were not the innocents they claimed within a matter of days after the blaze because "things weren't adding up".
Officers had to tread carefully in investigating their fears and used such tactics as the covert audio recordings to firm up their beliefs.
In the ensuing investigation it became clear that Philpott was the leader and instigator of the plan to set the fire, but it was not possible to ever know who poured the petrol and lit the match that started the blaze.
Information from the Allenton community was hard to come by, Mr Cotterill said, because of the individuals involved in the investigation.
Philpott had a certain notoriety and celebrity status because of his television appearances within some parts of the community, and people were also just wary of speaking out against the parents of six dead children, even if they had their suspicions.
Their arrests brought about a chain reaction, Mr Cotterill said.
"What we've ended up doing over the last 10 months is getting information on a drip-feed."
The eventual change of the charges from murder to manslaughter was the right decision, he added.
"Was the intention with malice and forethought to kill those kids? No actually, no the evidence isn't pointing to that.
"What the evidence is pointing to is that it was reckless behaviour, stupidity if you like, to set that fire."
The jury's verdicts have given him no cause to celebrate because the deaths of the children remain, and the case has been so terribly sorrowful.
He said: "This was an evil, stupid, shameful act which has resulted in the death of five of his own children.
"I will never ever be able to forgive them for that, to understand that, to have sympathy for them for that."
Mr Cotterill went on: "This has been the saddest case I've ever dealt with, it's the most tragic case I've ever dealt with."
"Personally I've found it very upsetting. I've become extremely angry at the needless loss of life.
"Six little kids there that have not got the chance to grow up. Five vacant chairs on the Monday morning at that primary school must have been horrendous not only for the teaching staff but for all the other little kids there as well.
"How do you explain that five of those Philpott children are not going to be turning up on Monday morning? And in fact, boys and girls, they're not going to be here Tuesday, or for any day thereafter because their mum and dad have chosen to light a fire at the bottom of the stairs that killed them."
He went on: "Who in their right mind is going to set a fire at the foot of the stairs, using petrol, knowing full well it's going to go straight up that stairwell?
"The duty as a parent, surely to goodness, is to look after your kids, make sure they're safe and keep them out of harm's way."