Cutler took one of the Harrow seats on the GLC at its first election and remained a member of it throughout its existence, one of only eight people to do so. His prominence at Middlesex made him well-known and he served as Deputy Leader under Sir Desmond Plummer when the Conservatives were in control from 1967. Plummer gave Cutler the Chairmanship of the Housing Committee which gave him responsibility for the GLC's hundreds of thousands of units of council housing. Cutler believed that local authorities had no role in housing, and instituted a scheme to allow tenants to buy their own homes at a discounted price – which later became one of the tenets of Thatcherism. He also forcibly transferred much of the GLC housing stock to the London Boroughs. Cutler was for many years a member of the Conservative Monday Club, and wrote a booklet in 1970 entitled Rents – Chaos or Commonsense? for the Club.
Leader of the GLC
When the Conservatives lost control of the GLC in 1973 and Sir Desmond Plummer resigned as their Leader in 1974, Cutler was chosen as his successor. He was a populist and a showman who delighted in stunts, and when he won the 1977 GLC elections he became a very flamboyant Leader. He was sceptical of the merits of the GLC, seeing it as "too big, too remote and too shadowy", and set up an inquiry under Sir Frank Marshall into its powers and existence; Marshall found enough to justify the continuation of the GLC. Cutler wanted to extend the Jubilee line into Docklands but was refused the money by the Labour Government. Investment on the London Underground was not substantial and decisions taken during his period of office have been much criticised subsequently for leading to poor infrastructure in the long term. Cutler was also noted for meddling in detailed Underground management, which London Transport Chairman Sir Peter Masefield had to persuade him to stop. He also made a bid to host the Olympic Games of 1988, being a sports fanatic, but the national government were not supportive of this. Horace Cutler was knighted in the 1979 Birthday Honours.
Loss of power
In the 1981 GLC elections, Cutler made a great deal of the fact that Andrew McIntosh was likely to be deposed by the much more left-wing Ken Livingstone if the Labour Party won. He concentrated on attacking Livingstone during the campaign, saying that he wished to establish a Marxist power-base in London. Nevertheless, Labour won, and McIntosh was duly voted out in favour of Livingstone. Cutler gave up the Conservative Leadership in 1982, and left politics when the GLC was abolished in 1986. He died at age 84 in 1997.