Leaving parliament was never going to be easy. Having entered the Commons at a relatively young age – I was 31 – I knew that a parliamentary existence would be strange, even weird.

I knew that I would never be a “lifer”. A long Commons career followed by a sinecure in the Lords was never for me. This was informed by an aversion not to prolonged public service – the career in the nuclear industry for which I have departed parliament is just as dedicated to public service – but to the culture in which politics in Westminster is undertaken. There is a lot wrong with parliament. I arrived with a healthy contempt for its culture, behaviours and practices; I leave with the knowledge that this contempt was correct.

As a young MP, I felt like Carraway, never like Gatsby. Still, leaving the Commons has taken a huge mental and emotional effort.

21 December 2016

The news of my resignation breaks a few hours early because of a leak. The ­Guardian’s north of England editor, Helen Pidd, brings forward the publication of our interview as a result. Within minutes, my phone explodes. Twitter is unusable. My email server begins to creak. I watch with mounting ­anxiety. Ignoring calls from journalists – many of them friends – I talk instead with my fellow MP John Woodcock.

In politics, you acquire a sixth sense for who would be with you in the trenches at the worst moments. John is such a person. I don’t remember the conversation; I just remember hanging up and crying. I ­shower, dress and head for my in-laws’ farm. When I open the door, there are bottles of champagne on the step. That night, trying to avoid the news, I learn that I was young, popular, brilliant and talented. It’s like being at my own funeral. I drink the champagne.

24 December

I receive a text from Jeremy Corbyn wishing me and my family well. I thank him for his warm words on my resignation.

9 January 2017

I’m en route to the Vogtle nuclear power plant near Atlanta, Georgia, as a guest of NuGen. At Vogtle, Georgia Power is building two AP1000 reactors – the same type as will be built in Copeland. This is a project to which I have devoted 12 years of my life – from writing nuclear policy with the Blair government to making sure that Copeland was chosen as a nuclear new-build site and working to ensure that successive governments maintained the policies underpinning the nuclear renaissance that the Blair-Brown administration began.

Clement Attlee’s Labour government created the nuclear industry, the last Labour government created the nuclear renaissance and I am leaving parliament to return to the nuclear industry – yet Labour will be forced to fight the by-election in my former seat amid allegations of being anti-nuclear. There is nothing new in post-truth politics. Lies have always had the power to seduce.

23 January

It’s my last week in parliament and I’ve made arrangements to see the whips. As I approach the whips’ office through the tearoom staircase, a colleague shouts: “It’s Steve McQueen!”

1 February

I leave my home in Whitehaven for Sellafield at 6.45am. As I drive through the frost, an iridescent light appears on the horizon: a new dawn has broken, has it not?

I collect my pass and enter a whirlwind of meetings, inductions and instructions. Everyone is generous, welcoming and warm. It is at this point that, for the first time, I am faced with irrefutable proof that I am no longer an MP. I am reminded of my parliamentary induction. Chief Whip Hilary Armstrong told us, “Get in the chamber . . . Don’t hide . . . Sink or swim . . .” New Labour was no place for a snowflake. I am reminded, too, of my induction by the House payroll and expenses administrators. A year before the expenses scandal shook Westminster, they informed me: “All we ask is that you don’t buy any antiques . . .”

2 February

As when I entered parliament for the first time, I don’t have a desk. I’m hot-desking, or hot-podding, or hot-cubing. I remind myself that, for now, I remain the Crown steward and bailiff of the Manor of Northstead.

I bump into a colleague from my first time in the nuclear industry. “All right?” he asks.

“Getting there,” I reply.

“You know what they’re saying, don’t you?” he continues.

“No. What?”

“‘The bloody ego has landed.’”

I walk away wondering if it’s now my role in life to remind people of films set in the Second World War.

3 February

It’s a Friday and it strikes me that I have no constituency surgery. Everyone around me has their head down, meeting targets, solving problems. This is a £2bn-a-year operation. There’s no room for Gatsby here. This is why my new role excites me.

The self-immolating stupidity of Brexit, combined with the complex and growing needs of my family, contributed to my decision to leave parliament. Most of all, though, it was the opportunity to work in this organisation and help to drive change within it and my community that caused me to make the switch. My former constituency can and should be at the centre of one of the fastest-growing parts of the UK economy in the years to come. A changing Sellafield and a dynamic industry will be at the heart of this, and time is of the essence.

20 February

The by-election in my former seat draws near and my time as the Crown steward is running out.

I am repeatedly approached by the media for comment and I duck every request. This is for someone else now and I wish my successor well. None of us is indispensable.