Complex sentence: The influx of British reinforcements was too late for HMS "Junon": on 13 December she had been cruising alone to the east of Antigua and been surprised by Francois Roquebert's squadron of four French frigates.
Split into simpler sentences: The influx of British reinforcements was however too late for HMS "Junon". On 13 December she had been cruising alone to the east of Antigua and been surprised by Francois Roquebert's squadron of four French frigates.