Just to follow this up, I have again tried <br><br>mapobj.setProjection(&#39;+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +datum=OSGB36 +units=m +no_defs&#39;); <br><br>but this still does not work.<br>
<br>mapobj.setWKTProjection(&#39;PROJCS[&quot;OSGB 1936 / British National Grid&quot;,GEOGCS[&quot;OSGB 1936&quot;,DATUM[&quot;OSGB_1936&quot;,SPHEROID[&quot;Airy 1830&quot;,6377563.396,299.3249646,AUTHORITY[&quot;EPSG&quot;,&quot;7001&quot;]],AUTHORITY[&quot;EPSG&quot;,&quot;6277&quot;]],PRIMEM[&quot;Greenwich&quot;,0,AUTHORITY[&quot;EPSG&quot;,&quot;8901&quot;]],UNIT[&quot;degree&quot;,0.01745329251994328,AUTHORITY[&quot;EPSG&quot;,&quot;9122&quot;]],AUTHORITY[&quot;EPSG&quot;,&quot;4277&quot;]],UNIT[&quot;metre&quot;,1,AUTHORITY[&quot;EPSG&quot;,&quot;9001&quot;]],PROJECTION[&quot;Transverse_Mercator&quot;],PARAMETER[&quot;latitude_of_origin&quot;,49],PARAMETER[&quot;central_meridian&quot;,-2],PARAMETER[&quot;scale_factor&quot;,0.9996012717],PARAMETER[&quot;false_easting&quot;,400000],PARAMETER[&quot;false_northing&quot;,-100000],AUTHORITY[&quot;EPSG&quot;,&quot;27700&quot;]]&#39;)<br>
<br>does work however, and is completing in roughly 4ms (with a premium for the first attempt ~ 50ms)<br><br>Compared to the 100-200ms I have been seeing for &#39;init=epsg:27700&#39; this is a significant improvement, especially as this method is used for every layer in a request, and my standard request is approx 18 layers (2 seconds per request has shrunk to 90ms).<br>
<br>Many thanks to all concerned for their help.&nbsp; Much appreciated.<br><br>I would still like to know how to do it via a setProjection method, but I now have an effective workaround.<br><br>Thanks<br><br>Rob<br>