Former English rugby star Jeremy Guscott believes the "mentally draining" impact of the British and Irish Lions' tour of New Zealand last year is partly to blame for England's recent slump in form.
England surrendered the Six Nations title after consecutive away defeats to Scotland (25-13) and France (22-16) and Ireland won the championship on Saturday (Sunday NZ time) after four wins from four.
Ireland have also subsequently leapfrogged England into second place in rugby's world rankings and Guscott, who played on three Lions tours (1989, 1993 and 1997), said the English players are feeling the tiring effects of the gruelling six-week tour which ended in an historic drawn series with the All Blacks.
Of the 41-man squad that first departed for New Zealand last June, 16 were English, 12 were Welsh, 11 were Irish, and there were three Scots.
"England are not not working hard enough and they're not working with enough intensity. The reason behind that is they look tired," Guscott wrote for the BBC.
"Mentally, going on a Lions tour and then coming back to a long domestic and international season makes a huge difference. The Lions is so big, I can't explain how mentally draining it is."
After returning home from New Zealand, most British and Irish players had less than a month off before beginning pre-season training for their club seasons.
England coach Eddie Jones admitted his side were "struggling" after losing the Six Nations title they won in 2016 and 2017.
Of the 23-man England squad that lost in Paris, 13 featured in the three-match series against the All Blacks last year.
"These days the players are constantly monitored by their club and country with the most advanced sports science methods, so the coaches should be able to tell if they're drained, and they shouldn't be picking them if that's the case," Guscott added.
"No player is ever going to say they're mentally drained, but as a player you don't realise it and that's where the management have to step in."