From 1973 Brookes was a member of ClwydArea Health Authority, where she served on the Family Practitioner Committee, and was also co-opted onto Clwyd County Council Social Services Committee. She was a member of the Council for Professions Supplementary to Medicine and had several voluntary sector posts in North Wales relating to the disabled and mentally handicapped.
European Parliament
At the 1979 European Parliament election, Brookes was elected as Conservative MEP for North Wales. She was a strong supporter of British membership of the European Communities and in 1981 at the Conservative Party conference moved a motion condemning the then Labour policy of leaving it; she argued that such a policy would leave Britain weak, friendless, isolated and bankrupt. She pointed to statistics about the economy and trade with Europe to claim that one job in three depended on Britain staying in.
Selection dispute
Brookes made a determined effort to be selected for the boundary changed constituency of Clwyd North West at the 1983 general election, over the claims of the sitting MPs for West Flintshire and Denbigh. The selection contest attracted national attention and Conservative Central Office decided to stay out of the dispute. On 6 March, Brookes won the selection vote in the Clwyd North West Conservative Executive, with Meyer describing the meeting as having been fixed and Morgan saying that speaking at the meeting was "like speaking to a nobbled jury". Conservative Party chairmanCecil Parkinson then intervened, arising out of a newspaper report that Brookes claimed Central Office put her forward for the nomination. When the Executive of Clwyd North West Conservative Association placed only Brookes' name before the general membership for adoption, Meyer won a High Court judgment that his name should also be offered. When the full membership met on 9 May 1983, Meyer was narrowly adopted.
Further political life
Brookes remained in the European Parliament. She protested in December 1983 over a BBC interview with the Welsh republican John Jenkins, who had been jailed for a bombing campaign at the time of the investiture of Charles, Prince of Wales. In the European Parliament she was a member of the Education and Agricultural Committees. She was defeated by the Labour Party candidate at the 1989 European Parliament elections. She remained involved in Welsh Conservative politics and in 1993 was chair of the Welsh Conservative Party, and proclaimed her support for John Major at a time when he was under fire from within the party. She was appointed Chair of the Welsh Consumer Council, but her re-appointment in 1994 went ahead despite criticism from the National Consumer Council that despite her ability, a non-political choice would be more appropriate. She was awarded the CBE in 1996. On 3 May 2013 she joined UKIP.
Car boot sales
Although retired, she was still considered newsworthy in 2003 when she won permission to hold more "car boot sales" on her land at Rhuddlan on 14 Saturdays in a year. She had in 2000 obtained permission to hold sales on 28 Sundays in a year, and also offered the land for use for fireworks displays and the National Eisteddfod of Wales.