This is the third group of martyrs executed in retaliation for the attempted invasion of England by the Spanish Armada.
Four of them are called "The Oaten Hill Martyrs" because they were executed on Oaten Hill in Canterbury. According to this website:
BLESSED EDWARD CAMPION
Edward Campion was the alias used by Father Gerard Edwards. He was born at Ludlow in Shropshire and studied at Oxford where he obtained a degree. This would indicate that he had subscribed to the new religion, since only those prepared to take the Oath of Supremacy, swearing on the Bible that the king was the rightful governor of the Church in England and so denying the authority of the Pope, could come down with a degree. He then became a servant to Gregory Fiennes, 8th Baron Dacres of the South. Baron Dacres was married to Anne Sackville, a member of a family with strong Catholic leanings. Gerard was reconciled to the Church at this time, and in February 1586 went to the English Seminary at Rheims. Here he adopted the name of Campion in order to associate himself more closely with St Edmund Campion, who had been martyred some years earlier. Because of his good education, his priestly training was shortened, and he was ordained in March 1587. A few days later he set sail for England, but after only a few weeks was arrested at Sittingbourne. He confessed he was a priest and boldly avowed that the religion now professed in England was heretical. He was then taken to London and imprisoned in the Marshalsea Prison in South London. Father Campion was examined again on 14th August,1588, and at the end of September he was sent to Canterbury for execution.
BLESSED CHRISTOPHER BUXTON
Christopher Buxton, a Derbyshire man, was born in 1562, and was educated at Tidewell Grammar School where one of his masters was Nicholas Garlick who was himself martyred for the Faith. In July 1582 Christopher arrived with two school-friends at Rheims. In 1584 he was sent to the English College in Rome where he was ordained on 26th October 1586. He had a lengthy and difficult journey across Europe, calling in at Rheims on his way to Dieppe. In September 1587 he crossed over to Kent, but was arrested there in November and taken to the Marshalsea prison. On 15th August 1588 Father Buxton was examined and then taken to Canterbury for trial and execution at the end of September. At his examination he admitted he was a priest.
BLESSED ROBERT WILCOX
Robert Wilcox was born in Chester in 1558 and entered the seminary at Rheims when he was twenty-five years old. He was ordained on 20th April 1585 and arrived in England on 7th june 1586. He was arrested almost immediately at Lydd in Kent, presumably where he landed. He, too, was sent to the Marshalsea where he was examined on 15th August 1588. Here he admitted he was a priest and was sent for trial with the others to Canterbury.
BLESSED ROBERT WIDMERPOOL
Robert Widmerpool was born in Nottinghamshire in 1560 and was at Oxford in 1578. There is no record that he graduated, an indication that he had remained a Catholic. A little later he obtained a post as a tutor with the Countess of Northumberland. In 1588 he was charged with hospitality towards priests and specifically with having introduced a priest into the house of the Countess. He was imprisoned in the Marshalsea, and was sent down with the others for trial and execution at Canterbury. It would seem that it was decided that the executions of Catholics should take place in significant local centres around London so that the example made by them would be felt as widely as possible.
The other locations that day were Chicester and Ipswich. The story of the Chicester martyrs is here. According to this blog, Blessed John Robinson was an older man:
BORN at Fernsby, Yorkshire, he lived for some time in the world in the married state, but on becoming a widower he went over to Rheims, was ordained, and sent on the Mission. He was a man of great simplicity and sincerity, and he used to say that " if he could not dispute for the faith as well as some of the others, he could die for it as well as the best." He was apprehended in the very port where he landed, and cast into the Clink prison. His fellow-prisoners, in respect to his age and probity, called him "Father," and he in return styled them his "bairns," and when they were sent off to be executed in different parts of the Kingdom, the good old man lamented for days exceedingly, until at last the warrant for his own execution arrived. To the bearer of the warrant he gave all his money, and on his knees gave God thanks. He was sent to suffer at Ipswich, a long journey taken on foot, but he refused to put on boots, as he said, " These feet of mine have never worn them, and they can well travel now without them, for they will be well repaid."