Context: The islands have been shaped by numerous glaciations during the Quaternary Period, the most recent being the Devensian.[citation needed] As this ended, the central Irish Sea was deglaciated and the English Channel flooded, with sea levels rising to current levels some 4,000 to 5,000 years ago, leaving the British Isles in their current form. Whether or not there was a land bridge between Great Britain and Ireland at this time is somewhat disputed, though there was certainly a single ice sheet covering the entire sea.

Question: What was the most recent glaciation that has shaped the British Isles?
Answer: Devensian

Question: What happened with the Devensian glaciation ended?
Answer: the English Channel flooded

Question: When did sea levels reach their current highth?
Answer: 4,000 to 5,000 years ago

Question: What covered the sea between Ireland and Great Britian during the last glacier?
Answer: a single ice sheet

Question: When did sea levels rise to prehistoric levels?
Answer: Unanswerable

Question: It is undisputed that there was a land bridge between Great Britain and what country?
Answer: Unanswerable

Question: Multiple sheets and layers of what covered the entire sea?
Answer: Unanswerable

Question: During which Period have the land bridges been shaped by glaciations? 
Answer: Unanswerable

Question: During this period, it is certain a land bridge existed between England and which country?
Answer: Unanswerable