While no historically significant events have taken place in Eastcote, there are links to past events in the history of Britain. One such example is of Lady Mary Bankes, who lived in Eastcote for a time, and led the defence of Corfe Castle in Dorset against the Roundheads during the English Civil War. Eastcote also housed an outstation of the Bletchley Park codebreaking activities during the Second World War, with several codebreaking computers in use. This operation became the precursor to GCHQ, which remained in Eastcote after the war until the department moved to purpose-built buildings in Cheltenham in 1952.
By the turn of the 20th century, the recorded population was around 600; this had reached for the ward in 2007.
Eastcote was originally recorded as Ascot, one of the three medieval tithings of the parish of Ruislip, along with Westcot and Norwood. Norwood, in the north of the parish, became Northwood; Westcot, in the west became Westcote (the main Ruislip village), and Ascot, in the east, became what is now Eastcote.
The Hawtrey family moved to Eastcote around 1525 after Ralph Hawtrey married Winifred Walleston. She lived in a cottage named "Hopkyttes", which the couple moved into and renamed Eastcote House. A dovecote was built by their son John, without applying for a licence from the manor, as was the custom at the time. After his death in 1593, his nephew Ralph Hawtrey applied for the licence, which was approved.
Ralph Hawtrey's only daughter became Lady Mary Bankes when she married Sir John Bankes, Chief Justice to Charles I As a Royalist, she defended their home in Dorset, Corfe Castle, against the Roundheads in 1643 at the time of the English Civil War. A plaque on the south wall of St Martin's Church in Ruislip commemorates her heroic act. Lady Bankes had also lived at Haydon Hall in Eastcote, and her name is remembered by the school in Ruislip Manor.
In 1565, a land survey was completed which recorded 62 houses in Eastcote, of which four were ruined.
The first Haydon Hall was built in 1630 for Lady Alice, the Dowager Countess of Derby, predominantly to allow her to store her possessions there. Lady Alice lived at Harefield Place, and purchased the land on which the hall was built from the Haydon family. The family appear in parish records from 1394 until 1562 when they sold a house on the site of Haydon Hall to William Nicholas.
Highgrove House was built in the 18th century but was destroyed by fire and rebuilt in 1879. Winston Churchill stayed there during his honeymoon and the Queen of Sweden was resident during the First World War.
At the turn of the 20th century, Eastcote was a small community with around 120 cottages and a population of around 600 people.
In 1930, the housing developers Comben & Wakeling purchased the Hawtrey family's land, which included Eastcote House and its grounds, with the plan for the new Eastcote Park Estate. The estate - comprising Abbotsbury Gardens, Devonshire Road, Lowlands Road, Deane Croft Road, Rushdene Road and The Chase - would have necessitated the demolition of Eastcote House until this was purchased by the Ruislip-Northwood Urban District Council in 1937 for public use. Haydon Hall was purchased by the local council in 1936 after the death of its owner, Mrs Bennett-Edwards.
The British government built a military hospital on land near Highgrove House during the war, in preparation for military casualties from the D-Day landings. They were not required for the role and were converted into barracks for Navy Wrens. Bletchley Park also established an outpost in surplus buildings on the site, which became known to staff as HMS Pembroke V. A total of 100 Bombe and Colossus codebreaker machines were used to decode German Enigma messages. The station closed shortly after the war ended in 1945, although the operations from Bletchley Park were re-established on the site in April 1946, under the new name of "Government Communications Headquarters". This closed when GCHQ moved and was established at Cheltenham. Between July 1952 and February 1954, GCHQ moved from Eastcote to new purpose-built buildings in Cheltenham.
In 1952, a number of new houses were built by Wimpeys Ltd in Newnham Avenue for the Ruislip-Northwood Urban District Council as part of their "no fines" scheme. The Minister for Housing and later Prime Minister, Harold Macmillan, attended.
In 1964, Eastcote House was demolished after it was declared structurally unsafe. Although the grounds including the walled garden, coach house and dovecote were retained for public use. Haydon Hall had also fallen into a state of disrepair and was demolished in 1967.
The RAF Eastcote site was sold for development to George Wimpey (now Taylor Wimpey) in 2007, with plans for the construction of 385 new homes. As of early 2011, 50% of the development had been completed, and the estate renamed Pembroke Park, in reference to HMS Pembroke V, the former name of the codebreaking operation during the Second World War.
In November 2011 the public house The Manor was refurbished and renamed "The Ascott", after the owners Greene King Brewery asked for public suggestions for a new name based on the local history of the area.