@anonymous93
The short answer is ‘no’.
The longer answer with reasons, results from studying the MHA, specifically S135. One need not be a lawyer to access and read the law via Google Searches or AI assisted searches.
The important words are ‘…any premises specified in the warrant in which that person is believed to be, and, if thought fit, to remove him to a place of safety with a view to the making of an application in respect of him under Part II of this Act, or of other arrangements for his treatment or care.’
But then ‘some’ people will navel gaze over the word ‘premises’. In such an exercise the meaning emerges in contrast to how S136 excludes certain kinds of dwellings.
When I worked in specialised service for the homeless in the capacity of a psychiatrist, a tent or cardboard box was not reasonably considered to be ‘premises’.
But who knows - things change all the time. Pragmatism and cultures stand to bend Parliament’s will.
Street homeless persons normally exist in places other than specified for exclusion in S136.
S136 (1A)The power of a constable under subsection (1) may be exercised where the mentally disordered person is at any place, other than—
(a) any house, flat or room where that person, or any other person, is living, or
(b) any yard, garden, garage or outhouse that is used in connection with the house, flat or room, other than one that is also used in connection with one or more other houses, flats or rooms.