Van der Graaf Generator were formed in 1967 Peter Hammill and Chris Judge Smith and were the first act signed by Charisma Records. Smith left the band before they released their first album having been functionally replaced on drums by Guy Evans. The band added Nick Potter (who left during the making of 1970's H To He Who Am the Only One) and firmed up a line-up of Hammill, Hugh Banton, David Jackson, Guy Evans.
As a quartet, they released toured extensively before splitting up in 1972. This period is called the 'classic' line-up and culminated in the release of Pawn Hearts one of the most celebrated albums of the VDGG cannon. The band did not gain a lot of traction except in Italy where they toured extensively. The US release of Pawn Hearts inclued the Beatles producer George Martin composition, Theme One which served as the fanfare for BBC Radio 1 a song which reached #1 on the charts in Italy.
Before, during and after the band's amicable split, the members often appeared on one another's solo releases. Ultimately, VDGG reformed in 1975. Three albums resulted from this 'first reunion' line-up, Godbluff, Still Life and World Record after which Bannon and Jackson left the band and a final release from this period The Quote Zone/The Pleasure Dome saw the return of Nick Potter and the addition of violinist Graham Smith (ex-String Driven Thing). The band split after the relase of this album in 1978.
They reunited in 2005 as a trio Hammill, Banton, and Evans.
Throughout it all, Peter Hammill maintained a very active solo career and the other musicians also release solo albums and albums in various combinations such as The Long Hello.
VDGG never achieved great commerical success (outside of Italy) but has an extremely faithful and hard-core following withing the universe of progressive rock fans.
There is a VDGG fan Website that may be of interest.