Chalk was born and brought up in the village of Foxcote, Gloucestershire, England. He attended independent school Winchester College before studying Modern History at Magdalen College, Oxford.
Following graduation, Chalk obtained a Graduate Diploma in Law from the City University London, and qualified as a barrister from the Inns of Court School of Law. During his legal career, he has prosecuted and defended in cases concerning terrorism, international fraud, and homicide. He has also advised and defended corporate clients, and prosecuted for HM Revenue and Customs and the Department of Business, Innovation and Skills. He represented journalists during the phone-hacking scandal. Chalk has provided counsel for the human rights lawyer Nasrin Sotoudeh, an Iranian prisoner of conscience.
Chalk was a councillor on the Hammersmith and Fulham council between 2006–2014, and chaired the Planning Committee for four years. He was elected as the Member of Parliament (MP) for Cheltenham in the 2015 general election. His victory in the constituency was the first for a Conservative Party candidate in 23 years.
In June 2015, Chalk was appointed to the Justice Select Committee, which scrutinises the government's decisions relating to the justice system, holding the seat until the dissolution of parliament. In addition to his role on the Justice Select Committee, Chalk was Chair of the All Party Parliamentary Group (APPG) on Pro Bono and Co- Chair of the APPG on Cycling. He was also the secretary of the APPG on Public Legal Education and the APPG for Highways and the vice chair of the APPG on Lyme Disease.
During the 2015 general election campaign, Chalk received support from the pro-hunting group Vote-OK, with members volunteering to deliver leaflets for him. In May 2017, Liberal Democrats candidate Martin Horwood said that Chalk was being actively supported by members of pro-hunting organisations Vale of White Horse Hunt, North Cotswold Hunt and Vote-OK, and questioned whether Chalk was concealing his position on fox hunting. Horwood noted that when asked to say yes or no to keeping the hunting ban, Chalk replied "free vote" in 2015 but replied "pass" in 2017.
Chalk held his seat in the 2017 general election with a reduced majority of 2,569.
Chalk has spoken in more debates than the average member of parliament. He has voted the same way as other Conservative MPs on a vast majority of issues. However, Chalk has sometimes differed from his colleagues, such as consistently voting against investigations into the Iraq war, while most Conservative MPs generally voted for. In December 2015, Chalk voted for UK airstrikes against Islamic State of Iraq and the Levant in Syria. In April 2016, he voted against a plan for Britain to accept 3,000 unaccompanied Syrian child refugees who had travelled to Europe. In February 2017, he voted for abandoning the Dubs amendment, an amendment to the Immigration Act 2016 to offer unaccompanied refugee children safe passage to Britain amidst the European migrant crisis.
Chalk alongside other MPs, including Richard Graham from the neighbouring Gloucester constituency, tabled a debate in parliament about stalking and sponsored a private member's bill, in order to raise the maximum sentence for stalking from five to ten years. An amendment to the Policing and Crime Act 2017 raised the maximum sentence for stalking to ten years. In announcing the amendment, Justice Minister Sam Gyimah praised Chalk and Graham's role in highlighting the issue.
Chalk supported remaining within the European Union prior to the United Kingdom European Union membership referendum in June 2016. He had expressed reservations about Britain's membership, even saying in his column in the local newspaper that "my heart says leave". Nevertheless, as outlined in the same column, Chalk decided that the perceived economic risk associated with a vote for Brexit was too great, and that "we need to hold our nose and stay". He supported the government by voting to trigger Article 50, which formally began the process of Britain's exit from the European Union. Chalk described his decision as a way of respecting the referendum result.
Chalk was among several Conservative candidates from the 2015 general election under investigation for breaking local campaign spending limits. This related to the use of "Battle Buses" during his election campaign, the costs of which were not declared by Chalk's campaign but were instead paid for by the Conservatives' national headquarters. Had the costs been declared the strict local spending limit would have been exceeded by £1,500. Gloucestershire Constabulary confirmed they had received a complaint in 2016 and he was under investigation at the time. In March 2017, the Electoral Commission fined the Conservative Party £70,000 for failing to accurately report campaign spending. In May 2017, The Crown Prosecution Service concluded their investigations into the allegations and determined that no Conservative Party candidates or officials would face charges. An investigation into the Conservative campaign in South Thanet however was to continue.