Complex sentence: However, Hertford wrote that Alexander was in the field with Arran's forces and retreated with them to Linlithgow, and before the 15 May Alexander had communicated with Hertford and mentioned that he planned to come to London as he could no longer abide in Scotland.
Split into simpler sentences: However, Hertford wrote that Alexander was in the field with Arran's forces and retreated with them to Linlithgow. Before 15 May, Alexander had communicated with Hertford and mentioned that he planned to come to London as he could no longer abide in Scotland.