Question: How many acres of land is the Box Moor Trust responsible for to include the parishes of Hemel Hempstead and Bovingdon?

Context paragraphs:
Magic Roundabout (Hemel Hempstead): The "Magic Roundabout" in Hemel Hempstead, Hertfordshire, England, is the familiar name given to the Plough roundabout.  The familiar name comes from the children's television programme, and is also used for a similar junction in Swindon and the M40 junction in Denham.  The official name relates to a former public house, called "The Plough Inn", which was between the junction of what is now Selden Hill and St Albans Road.  It has also been known as the Moor End Roundabout as it is adjacent to the part of Boxmoor nearest the town.  Before Hemel Hempstead became a New Town the roads met in a simple junction which was then replaced by a standard roundabout.

Roughdown Common: Roughdown Common is a 3.6 hectare biological Site of Special Scientific Interest in Hemel Hempstead in Hertfordshire.  The planning authority is Dacorum Borough Council.  The site is Common land, and it is owned by the Box Moor Trust having been officially brought by the trust in April 1886 from the Dean and Chapter of St Paul's.  It is part of the Chilterns Area of Outstanding Natural Beauty.  The Common is a steeply sloping chalk hill in south Hemel Hempstead.

Hemel Hempstead Swimming Club: Hemel Hempstead Swimming Club is a swimming club based in Hemel Hempstead, Hertfordshire, United Kingdom and was established in 1913.  Hemel Hempstead Swimming Club (HHSC) ranks as one of Hertfordshire's premier clubs.  The Club has in excess of 220 members from age 5 to Masters Level and their swimmers compete regularly in a wide range of competitions.

Hemel Hempstead railway station: Hemel Hempstead railway station is on the West Coast Main Line, on the western edge of the town of Hemel Hempstead, Hertfordshire, England.  The station is 24+1/2 mi north-west of London Euston on the West Coast Main Line.  Hemel Hempstead is managed by London Midland and all train services are operated by London Midland and Southern.

Watford General Hospital: Watford General Hospital is a 521-bed acute District General Hospital situated on Vicarage Road, Watford, Hertfordshire.  It is operated by West Hertfordshire Hospitals NHS Trust together with Hemel Hempstead General Hospital in Hemel Hempstead and the St Albans City Hospital in St Albans.

Hemel Storm: The Hemel Storm are a basketball team currently competing in Division 1 of the English National Basketball League.  The team is based in Hemel Hempstead, Hertfordshire and play their home games in the Hemel Hempstead Sportspace facility.  Over their short history, the club has been based in several locations across Hertfordshire and North London, before settling into their current, long-term home in 2010.

Gadebridge: Gadebridge is a district of Hemel Hempstead in Hertfordshire, UK, located north west of Hemel Hempstead old town.  It was developed from land that once formed part of Gadebridge House in the 1960s and centres on the Rossgate shopping parade.  Gadebridge Park is the largest green space in Hemel Hempstead.  A major Roman villa was discovered here at the time of its development (Gadebridge Park Roman Villa).  The population of the Dacorum ward (including Piccotts End) at the 2011 Census was 5,655.

Box Moor Trust: The Box Moor Trust is a charitable trust responsible for the management of nearly 500 acres of land within the parishes of Hemel Hempstead and Bovingdon, in Hertfordshire, England.  The Trust was officially founded in 1594 in order to ensure that the land in the Boxmoor area remained free for residents to use and enjoy.  As a result, almost all of the land that comprises the Box Moor Trust estate is open access, with just over a quarter being common land.

RAF Bovingdon: Royal Air Force Bovingdon or more simply RAF Bovingdon is a former Royal Air Force station located near the village of Bovingdon, 2.5 mi south of Hemel Hempstead, Hertfordshire and 2.5 mi southeast of Berkhamsted, Hertfordshire, England.

Bovingdon: Bovingdon is a large village in Hertfordshire, England, four miles southwest of Hemel Hempstead, and it is a civil parish within the local authority area of Dacorum.  It forms the largest part of the ward of Bovingdon, Flaunden and Chipperfield, which had a population of 4,600 at the 2001 census, increasing to 8,999 at the 2011 Census.

Supporting paragraphs: Box Moor Trust Bovingdon
Answer: 500 acres