Question: What did the organizer of a pop concert held at Knebworth House found in 1969?

Context paragraphs:
Knebworth Festival 1979: The Knebworth Festival 1979 consisted of two concerts performed by the English rock band Led Zeppelin and other artists at Knebworth House, Hertfordshire, England, in August 1979.

Concerts at Knebworth House: The Knebworth Festival is a recurring open air rock and pop concert held on the grounds of the Knebworth House in Knebworth, England.  The festival first occurred in 1974 when The Allman Brothers Band, The Doobie Brothers and other artists attracted 60,000 people.

Black Trip: The Black Trip album from Swiss heavy metal band Samael is a double DVD set which contains a concert held on Summer Breeze Festival (2002), a live concert held in Kraków, Poland, in 1996 during their "Passage" world tour and also a bootleg concert shot in Illinois (USA) during the "Ceremony of Opposites" tour.  There are also video clips for the songs "Jupiterian Vibe", "Infra Galaxia" and "Baphomet's Throne" as well as some interviews and footage shot at Woodhouse Studios during the making of the "Passage" album.

Abbey Aid: Abbey Aid was an open-air pop concert held at the Abbey Stadium, Cambridge, England in May 2006.  It was the first of its kind in Cambridge, targeting pop fans as opposed to the more established Cambridge Folk Festival which targets a substantially different audience.  It was a huge flop.

Knebworth: Knebworth is a village and civil parish in the north of Hertfordshire, England, immediately south of Stevenage.  The civil parish covers an area between the villages of Datchworth, Woolmer Green, Codicote, Kimpton, Whitwell, St Paul's Walden and Langley, and encompasses the village of Knebworth, the small village of Old Knebworth and Knebworth House.

Freddy Bannister: Freddy Bannister (sometimes written as Freddie Bannister) was a leading UK concert promoter during the 1960s and 1970s, and was the founder of the Bath Festival of Blues 1969, the Bath Festival of Blues and Progressive Music 1970 and the Knebworth festivals.

The London Rock and Roll Show: The London Rock and Roll Show was a concert held at Wembley Stadium in Wembley Park, London, England, on 5 August 1972.  It is often said to have been the first ever concert held at the stadium, but in fact the band Yes had performed in the Stadium on 13 July 1969.

Knebworth House: Knebworth House is a country house in the civil parish of Knebworth in Hertfordshire, England.  It is a Grade II* listed building.

Knebworth Park and Winter Green Railway: The Knebworth and Winter Green Railway was a narrow gauge railway built in the grounds of Knebworth House in 1972 as a tourist attraction.

Martin Elbourne: Martin Elbourne (born 19 January 1957 in Carlisle, Cumbria) is an English performing arts promoter.  Elbourne was brought up near the village of Knebworth, Hertfordshire.  His first job, at age fifteen, was working for the local stately home Knebworth House which in the mid-seventies became the biggest venue in the United Kingdom for outdoor shows and hosted bands such as Led Zeppelin, The Rolling Stones and Pink Floyd.

Supporting paragraphs: Freddy Bannister Concerts at Knebworth House
Answer: Bath Festival of Blues