Massive thanks to KingstonWinterfloods who very kindly agreed to archive their nearby cache that had been missing for a while, thereby freeing up the space for this one.
I've been thinking about placing a cache here for ages and, as I happened to be out and about placing another one along the river this morning, I thought that today was as good a day as any. In fact, I thought that it might prove to be a better day; when I checked the tide table, I saw that it was minus (how does that work?) 0.04m at Richmond at 9.55am. So, I thought that it might be possible to make this a much sought after 1/4.5. Perhaps if I'd arrived bang on low tide, then I could have been persuaded. However, at around 11.15am, the short journey was right on the limit of my chest waders. And the climb wasn't as easy as I was expecting (perhaps because I was wearing chest waders...). So, T5 it is. I don't think that it's possible to see the cache from the river bank, but you should be able to spot it once you've started the climb (it's a magnetic 35mm, although I might replace it with something a bit more hard-wearing in due course), so it's D1. As it happens, it now seems that 1/5 is rarer than 1/4.5 these days...
I think this is (currently) the most westerly "tidal Thames" cache, as the river ceases to be tidal just a few hundred metres upstream at Teddington Weir. However, I am not sure that it being "tidal" means a great deal. Even if you time your visit carefully, I don't think that you'll be able to stroll across on dry land. So, plan your visit and, depending on your preferred level of comfort, bring your specialist equipment of choice.
Tide tables can be found in the following link: http://www.pla.co.uk/Safety/Tide-Tables
Have fun, and take care. Given that it's the last stretch of tidal Thames, there is a lifeboat station very close by, but best not suffer the embarassment of having to call out the crew to rescue you...!!
Finally, I shouldn't need to say it but... In order to claim a find, you will need to go across and up. Watching from a distance whilst someone else signs your name in the log book doesn't count. Having someone else bring the log back for you to sign doesn't count (although it's fine if you then take it back and replace it). If you don't make it clear in your log that you've actually completed the challenge yourself, then you'll probably find that your log gets deleted... If you choose to write that you did when you didn't, then that is up to you and your conscience... It's a desirable D/T, so make sure you earn it!