How can avoid these spurious characters in my bash prompt?

Question

I have Fedora 20, and I would like to adapt the bash prompt to make it even more useful to me. At present my PS1 prompt is set by these lines in my ~/.bash_profile file:

 LP=" Last prompt at: "
 PS1="\[\033[s\033[0;0H\033[0;47m\033[K\033[1;34m[\$LP\]t\033[0m\033[u[<\u@\h \W>]\$ "
 echo

Which gives me a nice line at the top of the screen, with a grey bar (which does not show in this copy) and the time of the last prompt, thus:

[ Last prompt at: ]09:22:46
[<Harry@localhost ~>]$ 

Without the echo, when a terminal screen is opened, the prompt obscures the message on the top line. What the echo does is to echo its argument, so that when .bashrc. is run as a new terminal is opened, with no argument it nicely goes to a new line, leaving the top line alone. Subsequent prompts do not run .bashrc so the echo to a new line does not happen.

My question here concerns the "[ ]" brackets in the prompt round the Last prompt at: string. Please, how can I avoid these brackets appearing in the message displayed?

SOLVED
In response to @guido's answer. I had already tried just removing the square brackets, but then I lost the string completely. I note here that you have added a space after the LP, and that does indeed give me what I want, but I don't understand why the space is necessary: please could you add to your answer to explain that?

Answer 1

Just remove the square brackets from your PS1 (also there was a typo around \t):

LP=" Last prompt at: "
PS1="\[\033[s\033[0;0H\033[0;47m\033[K\033[1;34m\$LP \t\033[0m\033[u\][<\u@\h \W>]\$ "
echo

Answer 2

Guido's already answered your specific question, but just a note:

In addition, you could also set your scrolling region to be from the second line, so that scrolling doesn't erase that line.

PS1="\[\e[s\e[2;0r\e[H\e[0;47m\e[K\e[1;34m$LP\t\e[0m\e[u\]<\u@\h \W>\$ "

(though personally, I wouldn't to this kind of thing at the shell level, but for instance using screen and its hardstatus feature)