Sir Simon Milton: London's deputy mayor for policy and planning and Boris Johnson's chief of staff

Sir Simon Milton, deputy mayor of London for policy and planning and chief of staff to London Mayor Boris Johnson, was seen by many as "the man really responsible for running the capital" and perhaps more importantly as the "details man" who was able to make his boss's ideas a reality.

Milton arrived at a time when City Hall was in turmoil, following the premature departure of several important aides in the early days of Johnson's administration. He brought stability and was an instant success; he became the key official at City Hall, while Johnson was the flair, the ideas, the vigour and the dynamism. On many an awkward or complex issue, Johnson's inevitable response was, "Let's speak to Simon".

Described by Prime Minister David Cameron as "an extraordinarily talented politician", Milton, a quietly spoken, self-effacing man with more than 20 years in local government, was also tough, practical and persuasive and knew how to get things done. In the highly charged political world where mistrust among politicians is the norm, he was twice voted, by his peers, the most respected leader of local government in the country, while leading Westminster City Council between 2000 and 2008. The Council received four consecutive "Excellence" awards from the Audit Commission – no mean feat following the "homes for votes" scandal under Dame Shirley Porter's tenure. In 2007, he was elected chairman of the Local Government Association (LGA), where he won wide respect across the political spectrum.

Johnson described Milton as "a brilliant public servant... and hugely important in not only developing a new 'London Plan' but also securing many millions of pounds from developers for building new affordable housing in London." He was simply, "universally acknowledged to be brilliant at his job."

The son of Clive and Ruth, Simon Henry Milton was born in north-west London on 2 October 1961. He grew up in Cricklewood and attended St Paul's School, Hammersmith. His father, who was one of the German-Jewish children sent to Britain shortly before the Second World War on the Kindertransport, instilled the immigrant values of hard work and gratitude towards his adoptive country into his son.

Milton read history at Gonville and Caius College, Cambridge, where he became chairman of the University Conservative Association and president of the Union in 1983. He completed his Master's degree in professional studies at New York's Cornell University. He then started his working career at Sharaton's, his father's business, a chain of London patisseries. This period sharpened his political sensibilities – turning him into a young Thatcherite. He once described his anger at seeing the impact of high taxation on the business and his father's health.

In 1988, Milton was elected to Westminster City Council, in spite of the Conservatives being plagued by the "homes for votes" controversy during Dame Shirley Porter's leadership. During his early years on the council, Milton maintained a private sector career within a PR firm. Within three years, he was deputy leader of the council and by 2000 its leader for what became a record eight years. Milton immediately set a target for Westminster to become "Council of the Year", which it duly did in 2004, receiving the accolade from its peers. Westminster also won top ratings from the Audit Commission for four years in succession.

As leader, Milton kept Westminster's profile high, but moved it on from the Thatcherite image developed by Porter and her immediate successors. Despite its magnificent southern areas, much of the north of Westminster borough was, and remains, among the most deprived areas in Britain. Milton's administration recognised this and he tried some new approaches, such as bringing community groups, charities and businesses together to fight crime in bodies such as Civic Watch.

In addition, Milton oversaw the Paddington Basin initiative, which witnessed one of central London's biggest developments. Large swathes of wasteland and waterways around the station were to be redeveloped in what Milton called "Paddington First". His pledge was to ensure that the poorer residents would be able to get work on the construction sites for the regeneration programme. He was also involved with former London Mayor Ken Livingstone in the regeneration of Oxford Street.

Milton was knighted for services to local government in 2006, and a year later he succeeded Sandy Bruce-Lockhart as head of the LGA, a role he thrived in. With this position, it was expected that he might progress to a ministerial role in the House of Lords, if the Conservatives came to power. In May 2008, Mayor Johnson appealed to him for help after one of his deputy mayors had resigned due to financial irregularities. The opportunity to run London proved too enticing and he accepted, taking up his full-time post in September 2008.

In June 2009, he was appointed chief of staff to the Mayor with responsibility for managing the mayoral advisors, as well as the Greater London Authority budgets and administration. His experiences within local government had prepared him well as he set about trying to cut away the bureaucracy and red tape usually involved within local authorities. He continued to maintain good relations with council leaders from the LGA.

Milton's key role over the past three years was to oversee the process of revising the London Plan, the Mayor's key document in guiding the future of the city. The outer boroughs of London were given new priority in the process. Upon his appointment, Milton set out the terms of trade and used the Mayor's powers to refuse planning permission for the Howick Place building in Westminster because its developer was unwilling to pay a charge for the £16bn Crossrail scheme; the developer soon acquiesced. He even had the tact to persuade architects to take many storeys off their latest proposals for the sake of protecting London's views.

Milton had suffered ill health for a number of years. In 1990, he was diagnosed with leukaemia and had a bone-marrow transplant eight years later, using cells provided by his sister, Lisa. But he caught pneumonia while recovering which seriously damaged his lungs. He died after a short illness at the London Clinic, aged 49. He is survived by his civil partner, Robert Davis, his mother and his sister.

Martin Childs

Simon Milton, politician: born London 2 October 1961; civil partnership Robert Davis 2007; died London 11 April 2011.