Near this wall lies the body of John Howell A.M.
The son of Reynold Howell of Trenewyed, Gent.
He was sometime Rector of New Radnor but in the year of Trial 1691 was deprived
of all that he could not keep with a good conscience.
Who died Jan. 17th 1727, aged 70.
(A stone tablet in memory of a non-juring clergyman)
Searching online I have found the following:
Howell, Johns. Regin., of Trenewydd, co. Pembroke, pleb. Trinity Coll., matric. 20 March, 1673-4, aged 16; B.A. 29 Jan., 1677-8, M.A. 1680; brother of Arthur 1676. See Fasti, ii. 373.
Howell, Arthurs. Reginald, of Trenewydd, co. Pembroke, pleb. Christ Church, matric. 18 March, 1675-6, aged 16; died 17 April, 1676; brother of John 1674. See Gutch, i. 513. 
From: 'Alumni Oxonienses, 1500-1714: Horrobin-Hyte', Alumni Oxonienses 1500-1714: Abannan-Kyte (1891), pp. 748-784. URL: http://www.british-history.ac.uk/report.aspx?compid=117067 Date accessed: 08 March 2011.
From - http://melocki.org.uk/diocese/New_Radnor.html
1685 Apr 1 John Howell, M.A. patron - The king. previously John Hergest. cause of leaving - Death.
1690 Dec 13 James Gwyn, M.A. patron - The king and queen. previously John Howells. cause of leaving - Deprivation.
From - Crunwear Wills - http://www.genuki.org.uk/big/wal/PEM/Crunwear/Willsindex.html
1686 (ref - 16) Howel, John, New Radnor, Tutor, Guardian & Rector.
From - http://www.newadvent.org/cathen/11099a.htm
The name given to the Anglican Churchmen who in 1689 refused to take the oath of allegiance to William and Mary, and their successors under the Protestant Succession Act of that year. Their leaders on the episcopal bench (William Sancroft, Archbishop of Canterbury, and Bishops Francis Turner of Ely, William Lloyd of Norwich, Thomas White of Peterborough, William Thomas of Worcester, Thomas Ken of Bath and Wells, John Lake of Chichester, and Thomas Cartwright of Chester) were required to take the oath before 1 August, under pain of suspension, to be followed, if it were not taken by 1 February, by total deprivation. Two of them died before this last date, but the rest, persisting in their refusal, were deprived. Their example was followed by a multitude of the clergy and laity, the number of the former being estimated at about four hundred, conspicuous among whom were George Hickes, Dean of Worcester, Jeremy Collier, John Kettlewell, and Robert Nelson. A list of these Non-jurors is given in Hickes's "Memoirs of Bishop Kettlewell", and one further completed in Overton's "Non-jurors".