Inserting OS tiles using lisp routine

This routine was functional a couple of weeks ago. Now it's giving me the following error:

*Invalid*

; error: Function cancelled

I have tried changing the path of where the OS tiles are stored but nothing seems to be working. I would appreciate if someone could look into this.

(defun C:TQL ()
(command "setvar" "insunits" "0")
(command "setvar" 
"insunitsdefsource" "0")
(command "setvar" "insunitsdeftarget" 
"0")
(graphscr)
(command "expert" "5")
(command "ucs" "save" "UCS1" 
)
(command "ucs" "w" )    
(setq P1 (getpoint "\nPick suitable point "))    ;co ord
(setq PEAST (car P1))       ;eastings
(setq PNORTH (cadr P1))     ;northings
(setq PEASTF (rtos 
PEAST 2 0))      ;conversion to string
(setq PNORTHF (rtos PNORTH 2 0))     

(setq TQEAST (substr PEASTF 2 2))     ;parts of coords
(setq TQNORTH (substr PNORTHF 2 2))
(setq TQSQ (strcat TQEAST TQNORTH))   ;name of map
(setq TQEASTSQ (atoi 
(substr PEASTF 4 2)))
(setq TQNORTHSQ (atoi (substr PNORTHF 4 2)))



 (if (and (<= TQEASTSQ 50)(<= TQNORTHSQ 50))
 (setq MAP "SW")  )


 (if (and (<= TQEASTSQ 50)(> TQNORTHSQ 50))
 (setq MAP "NW")  )


 (if (and (> TQEASTSQ 50)(<= TQNORTHSQ 50))
 (setq MAP "SE")  )


 (if (and (> TQEASTSQ 50)(> TQNORTHSQ 50))
 (setq MAP "NE")  )


      ;
(setq REPLY (strcat 
"Co-ordinates give TQ" TQSQ MAP))
(princ REPLY)
(print)


(setq MPATH "D:/LB SOUTHWARK/Southwark CAD files/Latest 500m2 tiles")

;"//lbs-spatial01/spatialdata/Mapping/Raw_Data/OS MasterMap/Southwark and environs coverage/DWG/Latest 500m2 tiles/")    ;@  path for os maps
(setq DPATH (strcat MPATH "TQ" TQSQ MAP))


(command "-layer" "make" "xrefs" "")
(command "-xref" "O" DPATH "0,0" "" 
"" "")
(command "ucs" "restore" "UCS1" )
(command "-LAYER" "F" 
"*B_PT,*E_BY,*T_BY,*BMER,*G_PT,*PL_B,*GRID,*HTPT,*R_CL" "C" "252" "*tq*" "C" "251" "*road" "C" "250" "*buildout,buildpk" "")
(command "-LAYER" "F" "*8010010,*8010098,*8010321,*8010570,*8010571,*8010572,*8010573,*8010574,*8010575" "C" "252" "*G80*" "C" "251" "*8010021" "C" "250" "*8010001" "" )


(command "expert" "0")


)

Maybe the MPATH value should end in a path separator?

Thanks Roy_043 that did the trick.

Changed the following line:

(setq MPATH "D:/LB SOUTHWARK/Southwark CAD files/Latest 500m2 tiles")

to

(setq MPATH "D:/LB SOUTHWARK/Southwark CAD files/Latest 500m2 tiles/")