This could easily be so. The attack followed their common modus operandi. And certainly they have sympathizers in the UK, while the government pretends that all resident Muslims are moderate and loyal citizens.
“BREAKING: ISIS claims responsibility for London terror attack,” by Siobhan McFadyen, Express, March 23, 2017:
ISLAMIC STATE has claimed responsibility for the terror attack which killed three people and injured as many as 40 others in London yesterday.
The terror group made an annoucement [sic] in Arabic online today….