By Rachel Coughlan
Series Producer, Building the Olympic Dream
Watch episode three of Building the Olympic Dream, Laying the Foundations, on BBC Two on Wednesday, 18 March at 2100 GMT or afterwards on the BBC iPlayer.
When I first set foot on the 700-acre plot of land that will become the site for London's Olympic Park in 2012 I was surrounded by mud and rain.
It seemed that large piles of mud were just being shifted from one end of the park to another but I was informed that a target had been set to recycle 90% of all materials on site.
The soil was actually being taken to four huge soil washing plants where it would be washed, sieved and graded and used somewhere else on site.
Former model Celia Hammond was campaigning to collect all the wild cats left amongst the debris and when we caught up with her she had already removed 180
The site had been home to a number of businesses and factories, as well as having previously been a landfill tip.
So before any building work could begin, the land needed to be decontaminated, the waterways cleaned up and the site levelled.
I had seen the amazing graphics that revealed how the land would change over the next four years but at that moment it was hard to imagine.
And it brought home to me what a massive task lay before the Olympic authorities to get the park built and ready for the Games in just four years.
Blackjack was the last cat remaining on the construction site
The authorities were also committed to a different kind of clean-up - the removal of wildlife off the site.
Great crested newts - protected by law - were stalked at night and, where possible, bees, insects and toads were also being relocated.
We also found out that former model Celia Hammond was campaigning to collect all the wild cats left amongst the debris and when we caught up with her she had already removed 180.
Celia was being allowed access to the heavily protected site to lay baits and traps but much to her dismay her time was running out - and one elusive cat, Blackjack, had so far evaded her attempts to rescue him.
Obviously one cat couldn't be allowed to hold up the start of construction but Celia's cause caught the attention of the media and her access was extended.
Celia would tirelessly arrive every night on site determined to save the last remaining cat
I couldn't imagine that the Beijing authorities had been faced with this kind of situation.
Blackjack was regularly spotted by the security guards dodging machinery to get to Celia's food traps where he would take the food and scarper before the trapdoor shut.
Celia would tirelessly arrive every night on site determined to save the last remaining cat.
As the months moved on, so did the site. The mud shifters finally finished their job and the construction phase could begin.
I found myself standing in boots and hard hat in the middle of what will be the main stadium looking around and seeing the shape of the bowl emerging out of the soil.
Fast forward four years and where I was standing would be the focus of the world on opening night 2012.
Although an incredible amount of work had already been undertaken, there still seemed to be an awful lot more work to do.
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