Before the WW2 and even into the 1940's Rely-a-Bell and Auto Call (incorporating Ideal Alarms) had the business very much to themselves until the 1950's when Burgot started making serious inroads. After a significant rise in burglary after the Second World War, more alarm companies, encouraged by insurers, were established. Among these were Sentinel and Clarion Equipment.

A major influence on the intruder alarm industry at that time were the police who not only recommended the fitting of a system where property was perceived to be at high risk of being burgled, but also many forces, outside the major cities, allowed remote signalling systems to be connected directly into a Police Station. Later (circa 1968/72) the Police (through ACPO) were also responsible for demanding measures to be introduced in order to reduce the number of false alarms. This lead to the formation of regulatory bodies (e.g. NSI, SSAIB) and the compilation by the industry of a British Standard for the installation and maintenance of Intruder Alarms (BS 4737).

Also the Insurance Industry became very influential, requiring many policy holders to fit an intruder alarm (in addition to other measures) as a condition of insurance. By 1952 burglary had become a national concern of Insurers so much so that specialist surveyors were used to determine individual risk and identify measures to be taken to minimise any risk of burglary. This later lead to the formation of ABIS (Association of Burglary Insurance Surveyors), a major influence on the whole of the Security Industry.

 Auto-Call’s then major shareholder was Mr William McPhail. In the 1960's he acquired Automatic Fire Alarms (AFA), a company quoted on the London Stock Exchange and reversed his own company Auto-Call into it. He then set out on the acquisition trail and within a few short years had built a business that was the main competitor of the Rely-a-Bell and Burgot group.

The whole alarm industry grew quickly due to the number of ex Burgot, Rely-a-Bell and AFA employees who started their own local business many very successfully and some growing to a substantial size. Brock Alarms was one such company founded by Charlie Brock which was based in Hatton Garden, the London Jewellery quarter. Brocks grew to quite a size producing well known individuals such as Ron Cotton and Ray LeMonde, eventually they were acquired by Modern Alarms. Previously the industry had been more or less controlled through the sourcing of equipment which was manufactured by the main installers who were reluctant to sell to the competition. This was changed by manufacturers in the USA who were happy to sell to anyone and distributers of their equipment were set up in the UK. This exponential increase was a pattern followed throughout the country.

By 1966 there were some 57,000 intruder alarms capable of signalling alarm conditions to the police. Despite the formation of the NSCIA in 1972, and the addition of a further 168,000 remote signalling systems, insurance claims continued to grow.

 The intruder alarm market demonstrated substantial growth following the establishment of the NSCIA. This is demonstrated by the success of the first security industry exhibition and conference promoted by Victor Green (Paramount Publishing), the owner and editor of the Security Surveyor magazine, which he founded in May 1970 as the house journal of ABIS. He subsequently founded the International Security Exhibition and Conference (ISEC) in 1972 and the International Fire & Security Exhibition and Conference (IFSEC) in 1974 and an industry wide Golf Tournament.

Modern Alarms founded by Dennis Smith and Ron Jones in Birmingham but under the guidance of Canadian entrepreneur Tom Buffett and MD Mike Hawker, mainly through acquisition became at one stage the largest installer in the UK. In 1972 Arthur Bishop and Ron Ruff left Chubb to join Modern Alarms to expand the business in London and the south. At about the same time Shield Alarms based in Clerkenwell and run by Mike Cahalane and John Harris became one of the largest London installers.

Chubb Alarms reaction to the increase in competition combined with a difficult 1970's economic period, was to introduce a 1% sales commission paid on top of the salaries of the surveyors, who were responsible for designing, estimating and specifying the security systems.

The role of salesman was added to their job description and their title changed to "Sales Surveyors". Organising these changes was John Redfern the Sales Manager who had a hard task convincing the 80 plus surveyors, nationally, to accept a decrease in salary for the additional commission. Changes were made in advertising and promotion and Stuart McAinsh came across from Chubb & Sons Bank Division to improve and expand this area. Later Bob Tyley from GEC became Sales Director. He introduced "Sales Training" for the Sales Surveyors who had had little or no training in sales techniques.