Oliver St John, 5th Baron St John of Bletso

Oliver St John, 5th Baron St John of Bletso KB (1603 – 23 October 1642) was an English politician who sat in the House of Commons from 1624 to 1629 and in the House of Lords from 1639. He died fighting in the Parliamentary army in the English Civil War.

Education and family St John was the son of Oliver St John, 1st Earl of Bolingbroke and his wife Elizabeth Paulet, daughter of William Paulet. He was baptised on 2 April 1603. St John was admitted a fellow commoner of Queens' College, Cambridge on 3 November 1615, and was presumably the Oliver St John granted a passport to travel to Europe in June 1617. 2. Elizabeth St John married George Bennett of Cotsback 3. Arabella St John married Sir Edward Wyse of Sydenham 4. Dorothy St John married Francis Charlton of Apley Castle, Shropshire.

In the Commons In February 1624, his father arranged his return to Parliament as knight of the shire for Bedfordshire, replacing Oliver's uncle Sir Beauchamp St John.

On 27 April, St John certified to the House that there were no recusants holding office in his county, but does not otherwise appear in Parliamentary records. Re-elected for Bedfordshire in 1625, he was more active in that Parliament, serving on several legislative committees. He was appointed a justice of the peace for Bedford, Bedfordshire, and Hertfordshire that year.

The figure of £60,000 for his debts was given in a petition to the House of Commons in 1641; an enormous sum, if truthfully reported, for an heir apparent with a negligible estate of his own to offer as security. Two earlier petitions recited liabilities on his part of £6,900, still very significant, and he was also prosecuted as a surety for the debts of Sir Thomas Cheney, his uncle by marriage. As Clarendon avers, his debts did cause havoc for his sureties: some of the possessions of his uncle Sir Alexander St John were distrained by Lord St John's creditors, and Sir Capell Bedell, another surety, made a composition with Lord Bolingbroke to pay some of the debts to avoid the same fate.

On 21 November 1638, he obtained a passport to travel for three years under the alias of "St John Thompson", but the deception was discovered, and he was arrested under a warrant from Sir Francis Windebank on 21 December while lying ill at Rye. However, he was released or allowed to proceed, and spent the next two years in exile on the continent. From abroad, he petitioned for immunity from prosecution for debt, which was effectively granted when he was summoned to the House of Lords by writ of acceleration as Baron St John of Bletso, entering the House on 14 May 1641. His writ was said by Clarendon to have been granted with the object of composing his debts and reducing the turmoil among his sureties in Bedfordshire, and obtaining an adherent of the Royal party in the Lords; but St John showed no attachment to the King's cause. Indeed, he seems to have been largely preoccupied in defending himself from his creditors.

When the English Civil War broke out, he raised, presumably on his father's credit, a troop of horse and a regiment of foot for Parliament, in which Oliver Cromwell's eldest son, Oliver, served as cornet. Early in October 1642 he occupied Hereford on behalf of Parliament, fortified the town, and refused admittance to King Charles when he appeared there on 8 October. He then joined the army of the Earl of Essex. He was wounded at the Battle of Edgehill on 23 October 1642, captured by the Royalists, and according to Clarendon, died the next morning.