The MonoXXXX naming structure was introduced in year 2000, replacing the three classes in used previously, those being Class A, Mono Kent and Class B.   Class B was first introduced for 1000cc cars and ran from 1967 to 1973 inclusive.  Class B for Formula Ford 1600 cars was introduced in 1981, Mono Kent (referring to Ford's Kent engine)  grew out of that in 1985 and is now Mono1600.    After Mono Kents introduction, the Class B moniker was revised as a catchall for cars which were not a good fit into Class A or Mono Kent regulations, including an increasing number of motorcycle engined cars.   These were split into Mono1800 and Mono1200.  As the variety of cars competing widened, it became necessary to subdivide them into different classes to ensure that cars of roughly comparable performance were grouped together.

The class structure of any racing championship is built to promote close and fair racing against cars of similar specifications and speeds without forcing competitors into purchasing the latest specification chassis or engine, as the end result is too often "he who has the biggest chequebook wins".    The rules allow competitors to develop cars within limits; that being an aspect of Monoposto that has been part of its ethos since inception, and still allows drivers to race something they have designed and built themselves.   Occasionally classes are created to encourage cars that have for various external factors find themselves homeless, a place to race.    The Monoposto Board and Technical Committee monitors entries, looks at trends and the performance of cars, and adjusts the regulations and class structure accordingly.    The board recognises that despite their best intentions, some classes have not taken off, resulting in some classes being removed, but to the best of anyone's knowledge, no car that previously was eligible, has ever been turned away following class changes, nor have been rendered uncompetitive.

Further Notes:

[1] 2000 Formula was run as a separate class for full F3 engined specification cars (at 40mm ride height)in 2009, but this was merged with Mono2000 for 2010 due to lack of support.

[2] In 2007, all Mono 2000 cars which were eligible for the forthcoming 2000 Classic Class competed for the Classic Cup, it became a separate class the following season (2008).

[3] Mono ZTEC was a class for Formula Ford Zetecs to be run in standard FF Zetec guise. Tyres were free, but everything else was as per standard FFZ regs. It was split from Mono1800 for 2013, but only attracted one new car, all other competitors were already racing within Mono1800, therefore the classes were re-amalgamated for 2014.

[4] The Tiedeman Trophy was run as a series in 2013, and will run as an end of season mini-championship from 2014. The 2013 trophy was awarded to Jim Blockley as he took class win and fastest lap in all four races, but won the trophy on the tie breaker of being a member of the largest average class. Chris Dittmann and Jason Timms also matched Jim's results but their classes had, on average, fewer competitors.

[5] Mono DTEC was introduced in 2014 as a separate class for cars complying with Formula Ford Duratec regulations.  The Duratec era of professional Formula Ford was over as they had adopted the Ecoboost engine. Tyres were free, but everything else was as per Formula Ford Duratec regulations.   Poor uptake meant it was merged into Mono1800 for 2016.  The cars are still run as 'spec' cars but within the Mono1800 regulations.

[6] FR2000 was launched in 2017 - a class for the Tatuus built Formula Renault car used in the UK for many years, best known for the semi-professional Formula Renault BARC championship and the Formula Renault Championship supporting the BTCC, which saw Kimi Räikkönen, Lewis Hamilton, Paul di Resta and Heikki Kovalainen compete on their way to Formula 1.  Tatuus claim they have sold 850 cars around the world, so it was hoped it could be a strong addition to the grid...

[7] ...but sadly, despite assurances from owners/teams, the uptake was low, and so the FR2000 class was merged into the F3 class for 2019 season.    FR2000 cars are still welcome to race.

[8] Carl Jeanes raced under the pseudonym The Streaker after winning a £ 50 bet that he wouldn't run naked through the paddock at Thruxton in March 1974.  A photograph of this was published in the 30 years of Thruxton book, and was in Autosport magazine as well.

[9] Mono600 was a sub-class for 600cc Formula Honda Jedis.

[10] 2009 saw several new classes introduced. Mono1000 and 1400 was introduced, replacing 1200 Standard and Free and allowed the Suzuki Hayabusa engine to be used.    The classes were eventually merged to form MotoMono.

[11] 2016 saw a number of other adjustments to the class structure.     The 2000cc cars, formerly split over two classes were split into three.   Mono F3, Mono2000 and Mono2000 Classic.   Mono F3 was effectively a rebranding of Mono2000, which allowed the Mono2000 name to be used for a new class to house the rapid F4 / US FF2000 cars that had recently dominated 2000 Classic, but some of the older F3 cars that were too new to fall into Classic, but were no longer competitive against the latest F3 cars.

MotoMono was split into two following the domination of bike engined Dallara F3 cars.  Moto1400 was for carbon tubbed cars of up to 1400cc capacity and any space framed cars that wanted to run larger capacity bike engines.   Moto1000 was for spaceframed cars such as the popular Jedi or Speads family cars up to 1000cc capacity.  Carbon tubs is not permitted in Moto1000, although the use of carbon in non structural body panels is permitted.

[12] For 2024 the Mono F3 class was split into two.   Mono F3 A and Mono F3 B.    All F3 engined F3 cars from 2005 to 2011 were to race in Mono F3 A, alongside unrestricted Formula Renaults.   Tradtional Mono-spec engined cars from 2005 to 2011 and F3 engined cars from 1997 to 2004, as well as Mygale F4 Ecoboost and Formula Renault 2000 with 40mm restrictor.    2011 and earlier cars which previously raced in F3 Cup could race in Mono F3 A, although there was no longer a dispensation to run below the MSA minimum ride height of 40mm, and additionally the restrictor size was reduced by 1mm from 26mm to 25mm, two measures to reduce lap times slightly.