Former MP Craig Williams, who lives in Llanfair Caereinion, near Welshpool, has taken on the post as special advisor to Brexit Secretary Steve Barclay.
Mr Williams, who was born in Welshpool, has previous political experience and served as Conservative MP for Cardiff North from 2015 to 2017.
He also previously worked in the office of Montgomeryshire's current Conservative MP, Glyn Davies, when he was Assembly Member for the region.
The appointment comes at a crucial time, with Theresa May locked in discussions over an extension to the UK's Brexit deadline.
Mr Davies, said his former employee would be ideal for the role, taking on the biggest challenge in government.
He said: “I’ve known Craig since he left Welshpool High School to work with me in my Montgomeryshire constituency office when I was an Assembly Member.
"I always knew he was destined for great things. Over the last few years he has broadened his knowledge and honed his political skills working in the National Assembly, as a Cardiff City Councillor and as a Member of Parliament. I was really pleased when the irresistible ‘pull’ of Montgomeryshire brought him back to his family roots.
“At present there is no bigger job in Government than delivering on the referendum vote to leave the European Union, requiring political, negotiating and diplomatic skills, as well as determination. I could think of no-one better suited to this crucial task than Craig.
“Over the decades, Montgomeryshire has produced several influential politicians. I am pleased to have played a part in developing the career of another politician to take his place in the heart of Government.”
Meanwhile, North Shropshire Brexiteer Owen Paterson MP, has reiterated his call for the UK to leave the EU without a deal on Friday.
Mr Paterson, who has been a long-term critic of Theresa May's deal and has voted against it three times said it would be "worse than staying in".
The Conservative, who is a member of the pro-Brexit European Research Group, also said he could not see Mrs May continuing as Prime Minister and taking on the next stage of Brexit talks.
He said: "She has already said she intends to stand down, and I was in the committee room when that happened and you could just feel the residual power just disappear from her like a balloon deflating so whatever happens in the next few days it is not going to be her taking on the next stage of talks."